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Filed pursuant to Rule 424(b)(5)
Registration No. 333-220339

Subject to completion, dated September 5, 2017

This preliminary prospectus supplement relates to an effective registration statement under the Securities Act of 1933, but is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and we are not soliciting offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

Preliminary prospectus supplement
(to prospectus dated September 5, 2017)

12,500,000 shares

Common stock

We are offering 12,500,000 shares of our common stock, par value $0.001 per share, pursuant to this prospectus supplement and the accompanying prospectus. Our common stock is traded on the NASDAQ Global Select Market under the symbol "KTOS." On September 1, 2017, the last reported sale price of our common stock on the NASDAQ Global Select Market was $13.39 per share.

Certain of our directors and affiliated stockholders and entities may participate in this offering.

Investing in our common stock involves a high degree of risk. Please read "Risk factors" beginning on page S-13 of this prospectus supplement, on page 4 of the accompanying prospectus and in the documents incorporated or deemed incorporated by reference into this prospectus supplement before investing in our common stock.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

We have granted the underwriters an option for a period of 30 days to purchase up to an additional 1,875,000 shares of our common stock. If the underwriters exercise the option in full, the total public offering price will be $              , the total underwriting discounts and commissions payable by us will be $              , and our total proceeds, before expenses, will be $              .

The underwriters expect to deliver the common stock in book-entry form only, through the facilities of The Depository Trust Company, against payment in immediately available funds on or about                      , 2017.

Prospectus Supplement dated                     , 2017

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About this prospectus supplement

This prospectus supplement and the accompanying prospectus are part of a registration statement that we filed with the Securities and Exchange Commission ("SEC") utilizing a "shelf" registration process. This document is in two parts. The first part is this prospectus supplement, including the documents incorporated by reference, which describes the specific terms of this offering. The second part, the accompanying prospectus, including the documents incorporated by reference, provides more general information. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. We urge you to carefully read this prospectus supplement and the accompanying prospectus, and the documents incorporated by reference herein and therein, before buying any of the securities being offered under this prospectus supplement. This prospectus supplement may add to or update information contained in the accompanying prospectus and the documents incorporated by reference therein. To the extent that any statement we make in this prospectus supplement is inconsistent with statements made in the accompanying prospectus or any documents incorporated by reference therein that were filed before the date of this prospectus supplement, the statements made in this prospectus supplement will be deemed to modify or supersede those made in the accompanying prospectus and such documents incorporated by reference therein.

You should rely only on the information contained in this prospectus supplement and the accompanying prospectus, or incorporated by reference herein or therein. Neither we nor the underwriters (nor any of their affiliates) have authorized anyone to provide you with different information. No underwriter, dealer, salesperson or other person, including us, has authorized anyone to give you any information or to represent anything not contained in this prospectus supplement and the accompanying prospectus. You should not rely on any unauthorized information or representation. Neither we nor the underwriters (nor any of their affiliates) take any responsibility for, or can provide any assurance as to the reliability of, any information other than the information contained in this prospectus supplement and the accompanying prospectus, or incorporated herein or therein. This prospectus supplement is an offer to sell only the securities offered hereby, and only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information in this prospectus supplement and the accompanying prospectus is accurate only as of the date on the front of the applicable document and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the date of delivery of this prospectus supplement or the accompanying prospectus, or any sale of a security. Our business, financial condition, liquidity, results of operations and prospects may have changed since those dates.

Unless otherwise mentioned or unless the context requires otherwise, all references in this prospectus to "the Company," "we," "us," "our" and "Kratos" refer to Kratos Defense & Security Solutions, Inc., a Delaware corporation, and its consolidated subsidiaries.

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Risk factors

An investment in our common stock involves a substantial risk of loss. You should carefully consider the following risk factors and all other information contained herein as well as the information included or incorporated by reference in this prospectus supplement and the accompanying prospectus before you decide to invest in our common stock. The occurrence of any of the following risks could harm our business. In that case, the trading price of our common stock could decline, and you may lose all or part of your investment. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also impair our operations. You should also refer to the other information contained in this prospectus supplement and the accompanying prospectus or incorporated by reference herein or therein, including our financial statements and the notes to those statements, as well as the information contained in our Annual Report on Form 10-K for the fiscal year ended December 25, 2016, which is incorporated by reference herein, and the information set forth under the heading "Cautionary note regarding forward-looking statements."

Risks related to our business

The U.S. Government provides a significant portion of our revenue, and our business could be adversely affected by changes in the fiscal policies of the U.S. Government and governmental entities.

In fiscal 2016, 2015 and 2014, we generated 60%, 61% and 57%, respectively, of our total revenues from contracts with the U.S. Government (including all branches of the U.S. military and foreign military sales), either as a prime contractor or a subcontractor. We expect to continue to derive most of our revenues from work performed under U.S. Government contracts. See the Industry Update section in Part I, Item 2 "Management's Discussion and Analysis of Financial Condition and Results of Operations" contained within the Company's Quarterly Report on Form 10-Q for the fiscal year ended June 25, 2017, incorporated by reference herein, for a discussion of the current budgetary and funding constraints on U.S. Government spending and legislation enacted to reduce the U.S. federal deficit. As a result, we have experienced and expect to continue to experience reduced or delayed awards on some of our programs, with a related negative impact to our revenues, earnings and cash flows. Competitor bid protests also have become more prevalent in the current competitive environment resulting from decreased government spending, which has led to further contract award delays. In addition, any future changes to the fiscal policies of the U.S. Government and foreign governmental entities may decrease overall government funding for defense and homeland security, result in delays in the procurement of our products and services due to lack of funding, cause the U.S. Government and government agencies to reduce their purchases under existing contracts, or cause them to exercise their rights to terminate contracts at-will or to abstain from exercising options to renew contracts, any of which would have an adverse effect on our business, financial condition, results of operations and/or cash flows.

Significant delays or reductions in appropriations for our programs and U.S. Government funding more broadly may negatively impact our business and programs and could have a material adverse effect on our financial position, results of operations and/or cash flows.

U.S. Government programs are subject to annual congressional budget authorization and appropriation processes. For many programs, Congress appropriates funds on a fiscal year basis even though the program performance period may extend over several years. Consequently, programs are often partially funded initially and additional funds are committed only as Congress makes further appropriations. If we incur costs in excess of funds obligated on a contract, we may be at risk for reimbursement of those costs unless and until additional funds are obligated to the contract. We cannot predict the extent to which total

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funding and/or funding for individual programs will be included, increased or reduced as part of the annual budget process ultimately approved by Congress and the President or in separate supplemental appropriations or continuing resolutions, as applicable. Laws and plans adopted by the U.S. Government relating to, along with pressures on and uncertainty surrounding the federal budget, potential changes in priorities and defense spending levels, sequestration, the appropriations process, use of continuing resolutions (with restrictions, e.g., on new starts) and the permissible federal debt limit, could adversely affect the funding for individual programs and delay purchasing or payment decisions by our customers. In the event government funding for our significant programs becomes unavailable, or is reduced or delayed, or planned orders are reduced, our contract or subcontract under such programs may be terminated or adjusted by the U.S. Government or the prime contractor.

The budget environment, including sequestration as currently mandated, and uncertainty surrounding the appropriations processes, remain significant long-term risks. Considerable uncertainty exists regarding how future budget and program decisions will unfold, including the defense spending priorities of the new Administration and Congress and what challenges budget reductions (required by the Budget Control Act of 2011, as amended (the "Budget Control Act"), and otherwise) will present for the defense industry. It is likely budget and program decisions made in this environment would have long-term implications for our Company and the entire defense industry.

In March 2017, the debt ceiling was reached and the Treasury Department began taking "extraordinary measures" to finance the government. It is expected that in mid-to-late 2017 the U.S. Government will exhaust these available measures and Congress will need to raise the debt limit in order for the U.S. Government to continue borrowing money. If the debt ceiling is not raised, we may be required to continue to perform for some period of time on certain of our U.S. Government contracts even if the U.S. Government is unable to make timely payments.

Long-term funding for certain programs in which we participate may be reduced, delayed or cancelled. In addition, budget cuts globally could adversely affect the viability of our subcontractors and suppliers, and our employee base. While we believe that our business is well-positioned in areas that the DoD and other customers have indicated are areas of focus for future defense spending, the long-term impact of the Budget Control Act, other defense spending cuts, the debt ceiling and the ongoing fiscal debates remain uncertain.

Significant delays or reductions in appropriations; long-term funding under a continuing resolution; an extended debt ceiling breach or government shutdown; and/or future budget and program decisions, among other items, may negatively impact our business and programs and could have a material adverse effect on our financial position, results of operations and/or cash flow.

If we fail to establish and maintain important relationships with government agencies and prime contractors, our ability to successfully maintain and develop new business may be adversely affected.

Our reputation and relationship with the U.S. Government, and in particular with the agencies of the DoD and the U.S. intelligence community, are key factors in maintaining and developing new business opportunities. In addition, we often act as a subcontractor or in "teaming" arrangements in which we and other contractors bid together on particular contracts or programs for the U.S. Government or government agencies. We expect to continue to depend on relationships with other prime contractors for a portion of our revenue for the foreseeable future. Negative press reports regarding conflicts of interest, poor contract performance, employee misconduct, information security breaches or other aspects of our business, regardless of accuracy, could harm our reputation. Additionally, as a subcontractor or team member, we often lack control over fulfillment of a contract, and poor performance on the contract could tarnish our

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reputation, even when we perform as required. As a result, we may be unable to successfully maintain our relationships with government agencies or prime contractors, and any failure to do so could adversely affect our ability to maintain our existing business and compete successfully for new business.

Many of our contracts contain performance obligations that require innovative design capabilities, are technologically complex, require state-of-the-art manufacturing expertise, or are dependent upon factors not wholly within our control. Failure to meet these obligations could adversely affect our profitability and future prospects. Early termination of client contracts or contract penalties could adversely affect our results of operations.

We design, develop, and manufacture technologically advanced and innovative products and services, which are applied by our customers in a variety of environments. Problems and delays in development or delivery as a result of issues with respect to design, technology, licensing and intellectual property rights, labor, inability to achieve learning curve assumptions, manufacturing materials or components could prevent us from meeting requirements. Either we or the customer may generally terminate a contract as a result of a material uncured breach by the other. If we breach a contract or fail to perform in accordance with contractual service levels, delivery schedules, performance specifications, or other contractual requirements set forth therein, the other party thereto may terminate such contract for default, and we may be required to refund money previously paid to us by the customer or to pay penalties or other damages. Even if we have not breached, we may deal with various situations from time to time that may result in the amendment or termination of a contract. These steps can result in significant current period charges and/or reductions in current or future revenue. Other factors that may affect revenue and profitability include inaccurate cost estimates, design issues, unforeseen costs and expenses not covered by insurance or indemnification from the customer, diversion of management focus in responding to unforeseen problems, and loss of follow-on work.

If our subcontractors or suppliers fail to perform their contractual obligations, our performance and reputation as a contractor and our ability to obtain future business could suffer.

As a prime contractor, we often rely upon other companies as subcontractors to perform work we are obligated to perform for our customers. As we secure more work under certain of our contracts, we expect to require an increasing level of support from subcontractors that provide complementary and supplementary services to our offerings. We are responsible for the work performed by our subcontractors, even though in some cases we have limited involvement in that work. If one or more of our subcontractors fails to satisfactorily perform the agreed-upon services on a timely basis or violates U.S. Government contracting policies, laws or regulations, our ability to perform our obligations as a prime contractor or meet our customers' expectations may be compromised. In extreme cases, performance or other deficiencies on the part of our subcontractors could result in a customer terminating our contract for default. A termination for default could expose us to liability, including liability for the agency's costs of re-procurement, could damage our reputation and could hurt our ability to compete for future contracts.

We also are required to procure certain materials and parts from supply sources approved by the U.S. Government. The inability of a supplier to meet our needs or the appearance of counterfeit parts in our products could have a material adverse effect on our financial position, results of operations or cash flows.

Our earnings and profitability depend, in part, on subcontractor and supplier performance and product availability.

We rely on other companies to provide major components for our products. For instance, we build the airframe, electronics and flight control systems for our unmanned aerial systems. We rely on our suppliers

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to provide the engines and parachutes for landing the aircraft. Disruptions or performance problems caused by our subcontractors and suppliers, or a misalignment between our contractual obligations to our customers and our agreements with our subcontractors and suppliers, could have an adverse effect on our ability to meet our commitments to customers.

Our ability to perform our obligations on time could be adversely affected if one or more of our subcontractors or suppliers were unable to provide the agreed-upon products or materials or perform the agreed-upon services in a timely, compliant and cost-effective manner or otherwise to meet the requirements of the contract. Changes in economic conditions, including changes in defense budgets or credit availability, or other changes impacting a subcontractor or supplier (including changes in ownership or operations) could adversely affect the financial stability of our subcontractors and suppliers and/or their ability to perform. The inability of our suppliers to perform, or their inability to perform adequately, could also result in the need for us to transition to alternate suppliers, which could result in significant incremental cost and delay or the need for us to provide other resources to support our existing suppliers.

In connection with our U.S. Government contracts, we are required to procure certain materials, components and parts from supply sources approved by the customer. We also are facing increased and changing regulatory requirements, many of which apply to our subcontractors and suppliers. In some cases, there may be only one supplier for certain components. If a sole source supplier cannot meet our needs or is otherwise unavailable, we may be unable to find a suitable alternative.

Our procurement practices are intended to reduce the likelihood of our procurement of counterfeit, unauthorized or otherwise non-compliant parts or materials. We rely on our subcontractors and suppliers to comply with applicable laws and regulations, including regarding the parts or materials we procure from them; in some circumstances, we rely on certifications provided by our subcontractors and suppliers regarding their compliance. We also rely on our subcontractors and suppliers to effectively mitigate the risk of cyber and security threats or other disruptions with respect to the products and components they deliver to us and the information entrusted to them by us or our customers.

If we are unable to procure, or experience significant delays in subcontractor or supplier deliveries of, needed materials, components, intellectual property or parts; if our subcontractors or suppliers do not comply with all applicable laws and regulations; if the certifications we receive from them are inaccurate; or if what we receive is counterfeit or otherwise improper, it could have a material adverse effect on our financial position, results of operations and/or cash flows.

We face intense competition from many competitors that have greater resources than we do, which could result in price reductions, reduced profitability or loss of market share.

We operate in highly competitive markets and generally encounter intense competition to win contracts from many other firms, including mid-tier federal contractors with specialized capabilities, large defense contractors and IT services providers. Competition in our markets may increase as a result of a number of factors, such as the entrance of new or larger competitors, including those formed through alliances or consolidation, or the reduction in the overall number of government contracts. We may also face competition from prime contractors for whom we currently serve as subcontractors or teammates if those prime contractors choose to offer customer services of the type that we are currently providing. Recently, procurement award determinations have been based on lowest price, technically acceptable proposals. In addition, we may face competition from our subcontractors who, from time-to-time, seek to obtain prime contractor status on contracts for which they currently serve as a subcontractor to us.

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Many of our competitors have greater financial, technical, marketing and public relations resources, larger customer bases and greater brand or name recognition than we do. Such competitors may be able to utilize their substantially greater resources and economies of scale to, among other things:

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divert sales from us by winning very large-scale government contracts, a risk that is enhanced by the recent trend in government procurement practices to bundle services into larger contracts and the recent trend of making award determinations on a lowest price, technically acceptable basis;

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divert sales from us by the award of government contracts to our competitors who may be willing to bid at substantially lower prices;

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force us to charge lower prices; or

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adversely affect our relationships with current customers, including our ability to continue to win competitively awarded engagements in which we are the incumbent.

In the event that the market for products in our Unmanned Systems ("US") reporting segment expands, we expect that competition will intensify as additional competitors enter the market and current competitors expand their product lines. In order to secure contracts successfully when competing with larger, well-financed companies, we may be forced to agree to contractual terms that provide for lower aggregate payments to us over the life of the contract, which could adversely affect our margins. In addition, larger diversified competitors serving as prime contractors may be able to supply underlying products and services from affiliated entities, which would prevent us from competing for subcontracting opportunities on these contracts. If we lose business to our competitors or are forced to lower our prices, our revenue and operating profits could decline.

Our business is dependent upon our ability to keep pace with the latest technological changes.

The market for our services is characterized by rapid change and technological improvements. Failure to respond in a timely and cost-effective way to these technological developments would result in serious harm to our business and operating results. We have derived, and we expect to continue to derive, a substantial portion of our revenues from providing innovative engineering services and technical solutions that are based upon today's leading technologies and that are capable of adapting to future technologies. As a result, our success will depend, in part, on our ability to develop and market service offerings that respond in a timely manner to the technological advances of our customers, evolving industry standards and changing customer preferences.

We believe that, in order to remain competitive in the future, we will need to continue to invest significant financial resources to develop new offerings and technologies or to adapt or modify our existing offerings and technologies, including through internal research and development, acquisitions and joint ventures or other teaming arrangements. These expenditures could divert our attention and resources from other projects, and we cannot be sure that these expenditures will ultimately lead to the timely development of new offerings and technologies or identification of and expansion into new markets. Due to the design complexity of our products, we may, in the future, experience delays in completing the development and introduction of new products. Any delays could result in increased costs of development or deflect resources from other projects. In addition, there can be no assurance that the market for our products will develop or continue to expand or that we will be successful in newly identified markets as we currently anticipate. The failure of our technology to gain market acceptance could significantly reduce our revenues and harm our business. Furthermore, we cannot be sure that our competitors will not develop competing technologies that gain market acceptance in advance of our products.

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Additionally, the possibility exists that our competitors might develop new technology or offerings that might cause our existing technology and offerings to become obsolete. If we fail in our new product development efforts or our products or services fail to achieve market acceptance more rapidly as compared to our competitors, our ability to procure new contracts could be negatively impacted, which could negatively impact our results of operations and financial condition.

If the UAS and Unmanned Ground Systems ("UGS") markets do not experience significant growth, if we cannot expand our customer base or if our products do not achieve broad acceptance, then we may not be able to achieve our anticipated level of growth.

For the six months ended June 25, 2017, our US segment accounted for 10.7% of our total revenue. We cannot accurately predict the future growth rate or size of this market. Demand for our products may not increase, or may decrease, either generally or in specific markets, for particular types of products or during particular time periods. There are only a limited number of major programs under which the U.S. military, our primary customer, is currently funding the development or purchase of our UAS and UGS products. Although we are seeking to expand our US customer base to include foreign governments, domestic non-military agencies and commercial customers, we cannot assure that our efforts will be successful. The expansion of the UAS and UGS markets in general, and the market for our products in particular, depends on a number of factors, including the following:

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customer satisfaction with these types of systems as solutions;

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the cost, performance and reliability of our products and products offered by our competitors;

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customer perceptions regarding the effectiveness and value of these types of systems;

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limitations on our ability to market our US products and services outside the U.S. due to U.S. government regulations; and

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marketing efforts and publicity regarding these types of systems.

Even if UAS and UGS gain wide market acceptance in general, our specific products may not adequately address market requirements or may not gain market acceptance. If these types of systems generally, or our products specifically, do not gain wide market acceptance, then we may not be able to achieve our anticipated level of growth and our revenue and results of operations may suffer.

Loss of our General Services Administration ("GSA") contracts or GWACs could impair our ability to attract new business.

We are a prime contractor under several GSA contracts and GWAC vehicles. We believe that our ability to provide services under these contracts will continue to be important to our business because of the multiple opportunities for new engagements each contract provides. If we were to lose our position as prime contractor on one or more of these contracts, we could lose substantial revenues and our operating results could suffer. GSA contracts and other GWACs typically have a one or two-year initial term with multiple options exercisable at the government customer's discretion to extend the contract for one or more years. We cannot be assured that our government customers will continue to exercise the options remaining on our current contracts, nor can we be assured that our future customers will exercise options on any contracts we may receive in the future.

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Government contracts differ materially from standard commercial contracts, involve competitive bidding and may be subject to cancellation or delay without penalty.

Government contracts frequently include provisions that are not standard in private commercial transactions and are subject to laws and regulations that give the U.S. Government rights and remedies not typically found in commercial contracts, including provisions permitting the U.S. Government to:

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terminate our existing contracts;

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reduce potential future income from our existing contracts;

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modify some of the terms and conditions in our existing contracts;

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suspend or permanently prohibit us from doing business with the U.S. Government or with any specific government agency;

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impose fines and penalties;

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subject us to criminal prosecution;

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suspend work under existing multiple year contracts and related task orders if the necessary funds are not appropriated by Congress;

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decline to exercise an option to extend an existing multiple year contract; and

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claim rights in technologies and systems invented, developed or produced by us.

In addition, government contracts are frequently awarded only after formal competitive bidding processes, which have been and may continue to be protracted and typically impose provisions that permit cancellation in the event that necessary funds are unavailable to the government agency. Competitive procurements impose substantial costs and managerial time and effort in order to prepare bids and proposals for contracts that may not be awarded to us. In many cases, unsuccessful bidders for government contracts are provided the opportunity to formally protest certain contract awards through various agencies, administrative and judicial channels. We have experienced an increase in competitor bid protests on contracts on which we were the successful bidder due to the competitive environment resulting from decreased government spending. In addition, we have formally protested procurement awards in which we were not the initial successful bidder, but believed that the source selection process was flawed. The protest process may substantially delay a successful bidder's contract performance, result in cancellation of the contract award entirely and distract management. We may not be awarded contracts for which we bid, and substantial delays or cancellation of purchases may follow our successful bids as a result of such protests. We believe that this environment of protracted competitive bidding processes and competitor bid protests will continue.

Certain of our government contracts also contain "organizational conflict of interest" clauses that could limit our ability to compete for certain related follow-on contracts. For example, when we work on the design of a particular solution, we may be precluded from competing for the contract to install that solution. While we actively monitor our contracts to avoid these conflicts, we cannot guarantee that we will be able to avoid all organizational conflict of interest issues.

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We may not receive the full amounts estimated under the contracts in our backlog, which could reduce our revenue in future periods below the levels anticipated. This makes backlog an uncertain indicator of future operating results.

Backlog is typically subject to large variations from quarter to quarter and comparisons of backlog from period to period are not necessarily indicative of future revenues. The contracts comprising our backlog may not result in actual revenue in any particular period or at all, and the actual revenue from such contracts may differ from our backlog estimates. The timing of receipt of revenues, if any, on projects included in backlog could change because many factors affect the scheduling of projects. Cancellation of or adjustments to contracts may occur. Additionally, all U.S. Government contracts included in backlog, whether or not funded, may be terminated at the convenience of the U.S. Government. The failure to realize all amounts in our backlog could adversely affect our revenues and gross margins. As a result, our funded, unfunded and total backlog as of any particular date may not be an accurate indicator of our future earnings.

A preference for minority-owned, small and small disadvantaged businesses could impact our ability to be a prime contractor and limit our opportunity to work as a subcontractor on certain governmental procurements.

As a result of the Small Business Administration ("SBA") set-aside program, the federal government may decide to restrict certain procurements only to bidders that qualify as minority-owned, small, or small disadvantaged businesses. As a result, we would not be eligible to perform as a prime contractor on those programs and in general would be restricted to no more than 49% of the work as a subcontractor on those programs. An increase in the amount of procurements under the SBA set-aside program may impact our ability to bid on new procurements as a prime contractor, limit our opportunity to work as a subcontractor or restrict our ability to compete on incumbent work that is placed in the set-aside program.

U.S. Government in-sourcing could result in loss of business opportunities and personnel.

The U.S. Government has continued to reduce the percentage of contracted services in favor of more federal employees through an initiative called "in-sourcing." Over time, in-sourcing could have an adverse effect on our business, financial condition and results of operations. Specifically, as a result of in-sourcing, government procurements for services could be fewer and smaller in the future. In addition, work we currently perform could be in-sourced by the federal government and, as a result, our revenues could be reduced. Moreover, our employees could also be hired by the government. This loss of our employees would necessitate the need to retain and train new employees. Accordingly, the effect of in-sourcing or the continuation of in-sourcing at a faster-than-expected rate, could have an adverse effect on our business, financial condition, and results of operations.

Our business could be negatively impacted by security threats, including cybersecurity threats, and other disruptions.

Many of the systems we develop, install and maintain involve managing and protecting information involved in intelligence, national security and other sensitive or classified U.S. Government functions. We face various security threats, including cybersecurity threats, to gain unauthorized access to this sensitive information. Such threats can come from external as well as internal sources. We also face threats to the safety of our directors, officers, and employees; threats to the security of our facilities and infrastructure; and threats from terrorist acts. Although we utilize various procedures and controls to monitor these threats and mitigate our exposure to such threats, there can be no assurance that these procedures and controls will be sufficient in preventing security threats from materializing. If any of these events were to materialize, they could lead to the loss of sensitive information, critical infrastructure, personnel or

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capabilities essential to our operations and prevent us from being eligible for further work on sensitive or classified systems for U.S. Government customers. Further, any losses we incur from such a security breach could exceed the policy limits under our errors and omissions and product liability insurance. Any losses we incur, any damage to our reputation or any limitations on our eligibility for additional work resulting from a security breach could materially reduce our revenue and could have a material adverse effect on our business, financial condition and results of operations.

Cybersecurity attacks in particular are evolving and include, but are not limited to, malicious software, attempts to gain unauthorized access to data, and other electronic security breaches that could lead to disruptions in mission critical systems, unauthorized release of confidential or otherwise protected information and corruption of data. We have experienced cybersecurity attacks and may experience them in the future. These events could damage our reputation and lead to financial losses from remedial actions, loss of business, loss of proprietary and trade secret information or potential liability.

If we experience systems or service failure, our reputation could be harmed and our customers could assert claims against us for damages or refunds.

We create, implement and maintain IT solutions that are often critical to our customers' operations. We have experienced, and may in the future experience, some systems and service failures, schedule or delivery delays and other problems in connection with our work. If we experience these problems, we may:

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lose revenue due to adverse customer reaction;

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be required to provide additional services to a customer at no charge;

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cause customers to postpone, cancel or fail to renew contracts;

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receive negative publicity, which could damage our reputation and adversely affect our ability to attract or retain customers; and

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suffer claims for substantial damages.

We cannot ensure that provisions in our customer contracts will be legally sufficient to protect us if we are sued.

In addition, our errors and omissions and product liability insurance coverage may not be adequate, may not continue to be available on reasonable terms or in sufficient amounts to cover one or more large claims, or the insurer may disclaim coverage as to some types of future claims. The successful assertion of any large claim against us could seriously harm our business. Even if not successful, these claims may result in significant legal and other costs, be a distraction to our management and harm our reputation.

Our products are complex and could have unknown defects or errors, which may increase our costs, harm our reputation with customers, give rise to costly litigation, or divert our resources from other purposes.

Our products, including but not limited to unmanned vehicles, aerial targets, UAS and ballistic missile targets, are extremely complex and must operate successfully with complex products from other vendors. Despite testing, our products have contained defects and errors and may in the future contain defects or errors, or experience performance problems when first introduced, when new versions or enhancements are released, or even after these products have been used by our customers for a period of time. These problems could result in expensive and time-consuming design modifications or warranty charges, delays in the introduction of new products or enhancements, significant increases in our service and maintenance

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costs, diversion of our personnel's attention from our product development efforts, exposure to liability for damages, damaged customer relationships, and harm to our reputation, any of which could materially harm our results of operations. In addition, increased development and warranty costs could be substantial and could reduce our operating margins.

The existence of any defects, errors, or failures in our products or the misuse of our products could also lead to lawsuits against us, result in injury, death, or property damage, and significantly damage our reputation and support for our products in general.

Although we maintain insurance policies, we cannot provide assurance that this insurance will be adequate to protect us from all material judgments and expenses related to potential future claims or that these levels of insurance will be available in the future at economical prices or at all. A successful liability claim could result in substantial cost to us. Even if we are fully insured as it relates to a claim, the claim could nevertheless diminish our brand and divert management's attention and resources, which could have a negative impact on our business, financial condition, and results of operations.

Due to the volatile and flammable nature of certain components of our products and equipment, fires or explosions may disrupt our business or cause significant injuries, which could adversely affect our financial results.

The development and manufacture of certain of our products involves the handling of a variety of explosive and flammable materials as well as high power equipment. From time to time, these activities may result in incidents that could cause us to temporarily shut down or otherwise disrupt some manufacturing processes, causing production delays and resulting in liability for workplace injuries and/or fatalities. We have safety and loss prevention programs that require detailed reviews of process changes and new operations, along with routine safety audits of operations involving explosive materials, to mitigate such incidents, as well as a variety of insurance policies. However, we cannot ensure that we will not experience such incidents in the future or that any such incidents will not result in production delays or otherwise have a material adverse effect on our business and financial condition.

Our financial results may vary significantly from quarter to quarter.

We expect our revenue and operating results to vary from quarter to quarter. Reductions in revenue in a particular quarter could lead to lower profitability in that quarter because a relatively large amount of our expenses are fixed in the short-term. We may incur significant operating expenses during the start-up and early stages of large contracts and may not be able to recognize corresponding revenue in that same quarter. We may also incur additional expenses when contracts are terminated or expire and are not renewed.

In addition, payments due to us from our customers may be delayed due to billing cycles or as a result of failures of government budgets to gain congressional and administration approval in a timely manner. The U.S. Government's fiscal year ends September 30. If a federal budget for the next federal fiscal year has not been approved by that date in each year, our customers may have to suspend engagements that we are working on until a budget has been approved. Any such suspensions may reduce our revenue in the fourth quarter of the federal fiscal year or the first quarter of the subsequent year. The U.S. Government's fiscal year end can also trigger increased purchase requests from customers for equipment and materials. Any increased purchase requests we receive as a result of the U.S. Government's fiscal year end would serve to increase our third or fourth quarter revenue, but will generally decrease profit margins for that quarter, as these activities generally are not as profitable as our typical offerings.

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Additional factors that may cause our financial results to fluctuate from quarter to quarter include those addressed elsewhere in this "Risk factors" section and the following factors, among others:

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the terms of customer contracts that affect the timing of revenue recognition;

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variability in demand for our services and solutions;

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commencement, completion or termination of contracts during any particular quarter;

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timing of shipments and product deliveries;

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timing of award or performance incentive fee notices;

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timing of significant bid and proposal costs;

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the costs of remediating unknown defects, errors or performance problems of our product offerings;

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variable purchasing patterns under GSA contracts, GWACs, blanket purchase agreements and other indefinite delivery or indefinite quantity contracts;

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restrictions on and delays related to the export of defense articles and services;

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costs related to government inquiries;

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strategic decisions by us or our competitors, such as acquisitions, divestitures, spin-offs and joint ventures;

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strategic investments or changes in business strategy;

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changes in the extent to which we use subcontractors;

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seasonal fluctuations in our staff utilization rates;

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changes in our effective tax rate, including changes in our judgment as to the necessity of the valuation allowance recorded against our deferred tax assets; and

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the length of sales cycles.

Significant fluctuations in our operating results for a particular quarter could cause us to fall out of compliance with the financial covenants related to our debt, which if not waived, could restrict our access to capital and cause us to take extreme measures to pay down the debt, if any, under our $110.0 million Credit and Security Agreement, dated May 14, 2014 (the "Credit Agreement"). In addition, fluctuations in our financial results could cause our stock price to decline. See the risks and uncertainties related to our ability to raise additional capital below under "—Risks related to our operations—We may need additional capital to fund the growth of our business, and financing may not be available on favorable terms or at all."

Our margins and operating results may suffer if we experience unfavorable changes in the proportion of cost-plus-fee or fixed-price contracts in our total contract mix.

Although fixed-price contracts entail a greater risk of a reduced profit or financial loss on a contract compared to other types of contracts we enter into, fixed-price contracts typically provide higher profit opportunities because we may be able to benefit from cost savings and operating efficiencies. In contrast, cost-plus-fee contracts are subject to statutory limits on profit margins and generally are the least profitable of our contract types. Our U.S. Government customers typically determine what type of contract

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we enter into. Cost-plus-fee and fixed-price contracts in our federal business accounted for approximately 17% and 77%, respectively, of our federal business revenues for the six months ended June 25, 2017. To the extent that we enter into more cost-plus-fee or less fixed-price contracts in proportion to our total contract mix in the future, our margins and operating results may suffer.

Our cash flow and profitability could be reduced if expenditures are incurred prior to the final receipt of a contract.

We provide various professional services, specialized products, and sometimes procure equipment and materials on behalf of our customers under various contractual arrangements. From time to time, in order to ensure that we satisfy our customers' delivery requirements and schedules, we may elect to initiate procurement in advance of receiving final authorization from the government customer or a prime contractor. If our government or prime contractor customer's requirements should change or if the government or the prime contractor should direct the anticipated procurement to another contractor or if the equipment or materials become obsolete or require modification before we are under contract for the procurement, our investment in the equipment or materials might be at risk if we cannot efficiently resell them. This could reduce anticipated earnings or result in a loss, and negatively affecting our cash flow and profitability.

We have incurred and may continue to incur goodwill impairment charges in our reporting entities, which could harm our profitability.

As of June 25, 2017, goodwill represented approximately 51% of our total assets. We periodically review the carrying values of our goodwill to determine whether such carrying values exceed the fair market value. If impairment testing indicates that the carrying value of a reporting unit exceeds its fair value, the goodwill of the reporting unit is deemed impaired. Accordingly, an impairment charge would be recognized for that reporting unit in the period identified.

The identification and measurement of impairment involves the estimation of the fair value of reporting units. Accounting for impairment contains uncertainty because management must use judgment in determining appropriate assumptions to be used in the measurement of fair value. The estimates of fair value of reporting units are based on the best information available as of the date of the assessment, incorporate management assumptions about expected future cash flows and contemplate other valuation techniques. Future cash flows can be affected by changes in industry or market conditions, among other things.

Given the current market conditions and continued economic uncertainty in the U.S. defense industry, including sequestration and issues surrounding the national debt ceiling, our future revenues, profits and cash flows could be substantially lower than our current projections. Our ability to penetrate new international markets could also impact our current projections. Additional market factors could impact our projections and our ability to successfully develop new products and platforms. For example, our US reporting unit forecasts include the successful completion of certain performance criteria on new unmanned systems platforms, and acceptance of new unmanned systems platforms on a technical basis as well as from a political and government budgetary standpoint. In addition, market-based inputs to the calculations in the impairment test, such as weighted average cost of capital, and market multiples, could also be negatively impacted. Such circumstances may result in the future deterioration of the fair value of our reporting units and an impairment of our goodwill. Due to continual changes in market and general business conditions, we cannot predict whether, and to what extent, our goodwill and long-lived intangible assets may be impaired in future periods. Any resulting impairment loss could harm our profitability and financial condition.

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Failure to properly manage projects may result in additional costs or claims.

Our engagements often involve large scale, highly complex projects. The quality of our performance on such projects depends in large part upon our ability to manage the relationship with our customers and to effectively manage the project and deploy appropriate resources, including third-party contractors and our own personnel, in a timely manner. Any defects or errors or failure to meet customers' expectations could result in claims for substantial damages against us. Our contracts generally limit our liability for damages that arise from negligent acts, errors, mistakes or omissions in rendering services to our customers. However, we cannot be sure that these contractual provisions will protect us from liability for damages in the event we are sued. In addition, in certain instances, we guarantee customers that we will complete a project by a scheduled date. If the project experiences a performance problem, we may not be able to recover the additional costs we will incur, which could exceed revenues realized from a project. Finally, if we underestimate the resources or time we need to complete a project with capped or fixed fees, our operating results could be adversely affected.

We use estimates when accounting for contracts, and any changes in such estimates could have an adverse effect on our profitability and our overall financial performance.

When agreeing to contractual terms, our management makes assumptions and projections about future conditions and events, many of which extend over long periods. These projections assess the productivity and availability of labor, complexity of the work to be performed, cost and availability of materials, impact of delayed performance and timing of product deliveries. Contract accounting requires judgment relative to assessing risks, estimating contract revenues and costs, and making assumptions for schedule and technical issues. Due to the size and nature of many of our contracts, the estimation of total revenues and costs at completion is complicated and subject to many variables. For example, assumptions are made regarding the length of time to complete a contract since costs also include expected increases in wages, prices for materials and allocated fixed costs. Similarly, assumptions are made regarding the future impact of our efficiency initiatives and cost reduction efforts. Incentives, awards or penalties related to performance on contracts are considered in estimating revenue and profit rates and are recorded when there is sufficient information to assess anticipated performance. Suppliers' assertions are also assessed and considered in estimating costs and profit rates.

Because of the significance of the judgment and estimation processes described above, it is possible that materially different amounts could be obtained if different assumptions were used or if the underlying circumstances were to change. Changes in underlying assumptions, circumstances or estimates may have a material adverse effect upon the profitability of one or more of the affected contracts, future period financial reporting and performance.

Our ability to utilize our net operating loss carryforwards and certain other tax attributes may be limited.

Federal and state income tax laws impose restrictions on the utilization of net operating loss ("NOL") and tax credit carryforwards in the event that an "ownership change" occurs for tax purposes, as defined by Section 382 of the Internal Revenue Code of 1986, as amended. We believe we underwent an ownership change in March 2010 that limited the Company's federal annual utilization of NOL carryforwards. If the entire limitation amount is not utilized in a year, the excess can be carried forward and utilized in future years. For the fiscal year ended December 25, 2016, there was no impact of such limitations on the income tax provision since the amount of taxable income did not exceed the cumulative annual limitation amount. In addition, future equity offerings or acquisitions that have equity as a component of the purchase price could also cause an "ownership change." If and when any other "ownership change" occurs, utilization of the NOL or other tax attributes may be further limited.

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We expect to incur substantial research and development costs and devote significant resources to identifying and commercializing new products and services, which could significantly reduce our profitability and may never result in revenue to us.

Our future growth depends on penetrating new markets, adapting existing products to new applications, and introducing new products and services that achieve market acceptance. We plan to incur substantial research and development costs as part of our efforts to design, develop and commercialize new products and services and enhance existing products. We spent $8.5 million, or 2.4% of our revenue, in the six months ended June 25, 2017, on internally funded research and development activities. We believe that there are significant investment opportunities in a number of business areas. Because we account for research and development as an operating expense, these expenditures will adversely affect our earnings in the future. Further, our research and development programs may not produce successful results, and our new products and services may not achieve market acceptance, create additional revenue or become profitable, which could materially harm our business, prospects, financial results and liquidity.

Risks related to our operations

We may need additional capital to fund the growth of our business, and financing may not be available on favorable terms or at all.

We currently anticipate that our available capital resources, including the cash we raised in our recent equity offering, amounts available under our Credit Agreement and operating cash flow, taken together with the proceeds from this offering, will be sufficient to meet our expected working capital and capital expenditure requirements for at least the next 12 months. However, these resources may not be sufficient to fund the long-term growth of our business. If we determine that it is necessary to raise additional funds, either through an expansion or refinancing of our Credit Agreement or through public or private debt offerings or additional equity financings, additional financing may not be available on terms favorable to us, or at all. Disruptions in the capital and credit markets may continue indefinitely or intensify, which could adversely affect our ability to access these markets. Limitations on our borrowing base contained in our Credit Agreement may limit our access to capital, and we could fall out of compliance with financial and other covenants contained in our Credit Agreement which, if not waived, would restrict our access to capital and could require us to pay down any then-existing debt under the Credit Agreement. Our lenders may not agree to extend additional or continuing credit under our Credit Agreement or waive restrictions on our access to capital. If adequate funds are not available or are not available on acceptable terms, we may not be able to take advantage of available opportunities, develop new products or otherwise respond to competitive pressures and our business, operating results or financial condition could be materially adversely affected.

We might not succeed in our strategies for acquisitions and dispositions.

We have in the past and may, in the future, acquire additional businesses that we believe could complement or expand our business or increase our customer base. Integrating the operations of acquired businesses successfully or otherwise realizing any of the anticipated benefits of acquisitions, including anticipated cost savings and additional revenue opportunities, involves a number of potential challenges. The failure to meet these integration challenges could seriously harm our financial condition and results of operations. Realizing the benefits of acquisitions depends in part on the integration of operations and personnel. These integration activities are complex and time-consuming, and we may encounter unexpected difficulties or incur unexpected costs, including:

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our inability to achieve the operating synergies anticipated in the acquisitions;

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diversion of management attention from ongoing business concerns to integration matters;

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difficulties in consolidating and rationalizing IT platforms and administrative infrastructures;

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complexities associated with managing the geographic separation of the combined businesses and consolidating multiple physical locations where management may determine consolidation is desirable;

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difficulties in integrating personnel from different corporate cultures while maintaining focus on providing consistent, high quality customer service;

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difficulties or delays in transitioning U.S. Government contracts pursuant to federal acquisition regulations;

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challenges in demonstrating to customers of Kratos and to customers of acquired businesses that the acquisition will not result in adverse changes in customer service standards or business focus;

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possible cash flow interruption or loss of revenue as a result of change of ownership transitional matters; and

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inability to generate sufficient revenue to offset acquisition costs.

Acquired businesses may have liabilities or adverse operating issues that we fail to discover through due diligence prior to the acquisition. In particular, to the extent that prior owners of any acquired businesses or properties failed to comply with or otherwise violated applicable laws or regulations, or failed to fulfill their contractual obligations to the U.S. Government or other customers, we, as the successor owner, may be financially responsible for these violations and failures and may suffer reputational harm or otherwise be adversely affected. Acquisitions also frequently result in the recording of goodwill and other intangible assets that are subject to potential impairment in the future that could harm our financial results. In addition, if we finance acquisitions by issuing debt or equity securities, our existing stockholders may be diluted, which could affect the market price of our stock. Acquisitions and/or the related equity financings could also impact our ability to utilize our NOL carryforwards. As a result, if we fail to properly evaluate acquisitions or investments, we may not achieve the anticipated benefits of any such acquisitions, and we may incur costs in excess of what we anticipate. Acquisitions frequently involve benefits related to integration of operations. The failure to successfully integrate the operations or otherwise to realize any of the anticipated benefits of the acquisition could seriously harm our results of operations.

We also evaluate from time to time the potential disposition of assets or businesses that may no longer meet our growth, return and/or strategic objectives.

If we are unable to manage our growth, our business and financial results could suffer.

Sustaining our growth has placed significant demands on our management, as well as on our administrative, operational and financial resources. For us to continue to manage our growth, we must continue to improve our operational, financial and management information systems and expand, motivate and manage our workforce. Additionally, our future financial results depend in part on our ability to profitably manage our growth on a combined basis with the businesses we have acquired and those we may acquire in the future. If we are unable to manage our growth while maintaining our quality of service and profit margins, or if new systems that we implement to assist in managing our growth do not produce the expected benefits, our business, prospects, financial condition or operating results could be adversely affected.

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The loss of any member of our senior management could impair our relationships with U.S. Government customers and disrupt the management of our business.

We believe that the success of our business and our ability to operate profitably depends on the continued contributions of the members of our senior management. We rely on our senior management to generate business and execute programs successfully. In addition, the relationships and reputation that many members of our senior management team have established and maintain with U.S. Government personnel contribute to our ability to maintain strong customer relationships and to identify new business opportunities. The loss of any member of our senior management could impair our ability to identify and secure new contracts, to maintain good customer relations and to otherwise manage our business.

If we fail to attract and retain skilled employees or employees with the necessary national security clearances, we might not be able to perform under our contracts or win new business.

The growth of our business and revenue depends in large part upon our ability to attract and retain sufficient numbers of highly qualified individuals who have advanced technical and/or engineering skills. These employees are in great demand and are likely to remain a limited resource in the foreseeable future. In addition, certain U.S. Government contracts require us, and some of our employees, to maintain national security clearances. Obtaining and maintaining national security clearances for employees involves a lengthy process, and it is difficult to identify, recruit and retain employees who already hold national security clearances. Further, some of our contracts contain provisions requiring us to staff an engagement with personnel that the customer considers key to our successful performance under the contract. In the event we are unable to provide these key personnel or acceptable substitutions, the customer may terminate the contract. As a result, if we are unable to recruit and retain a sufficient number of qualified employees, we may lose revenue and our ability to maintain and grow our business could be limited.

Moreover, in a tight labor market our direct labor costs could increase or we may be required to engage large numbers of subcontractor personnel, which could cause our profit margins to suffer. Conversely, if we maintain or increase our staffing levels in anticipation of one or more projects and the projects are delayed, reduced or terminated, we may underutilize the additional personnel, which would increase our general and administrative expenses, reduce our earnings and possibly harm our results of operations.

We are subject to the requirements of the National Industrial Security Program Operating Manual for our facility security clearance, which is a prerequisite to our ability to perform on classified contracts for the U.S. Government.

A facility security clearance is required for a company to perform on classified contracts for the DoD and certain other agencies of the U.S. Government. Security clearances are subject to regulations and requirements including the National Industrial Security Program Operating Manual ("NISPOM"), which specifies the requirements for the protection of classified information released or disclosed in connection with classified U.S. Government contracts.

We require certain facility and personnel security clearances to perform our classified U.S. Government related business. As such, we must comply with the requirements of the NISPOM and any other applicable U.S. Government industrial security regulations. If we were to violate the terms and requirements of the NISPOM or any other applicable U.S. Government industrial security regulations (which apply to us under the terms of classified contracts), any of our cleared facilities could lose its facility security clearance. We cannot be certain that we will be able to maintain our facility security clearances. If for some reason one or more of our facility security clearances is invalidated or terminated, we would not be able to continue to perform on classified contracts at that facility and would not be able to enter into new classified contracts, which could adversely affect our revenues. Failure to comply with the NISPOM or other security

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requirements may subject us to civil or criminal penalties, loss of access to classified information, loss of a U.S. Government contract, or potentially debarment as a government contractor.

We may be unable to realize any benefit from our cost reduction and restructuring efforts and our profitability may be hurt or our business otherwise might be adversely affected.

We have engaged in cost reduction and restructuring activities in the past, including the recent restructuring actions in the modular systems and public safety businesses, and we may engage in other cost reduction restructuring activities in the future. These types of cost reduction and restructuring activities are complex. If we do not successfully manage our current cost reduction and restructuring activities, or any other cost reduction and restructuring activities that we may take in the future, any expected efficiencies and benefits might be delayed or not realized, and our operations and business could be disrupted. In addition, the costs associated with implementing cost reduction and restructuring activities might exceed expectations, which could result in additional future charges.

Risks related to our international operations

Revenues derived from our international business could be subject to global economic downturn and hardship.

Our international business represents approximately 10% of our total revenue for the six months ended June 25, 2017, which may be impacted by changes in foreign national priorities and government budgets and may be further impacted by global economic conditions and fluctuations in foreign currency exchange rates. Continued international economic uncertainty and reductions in consumer spending may result in reductions in our revenue. Additionally, disruptions in international credit markets may materially limit consumer credit availability and restrict credit availability of our customers. Any reduction in international sales of our solutions resulting from reductions in consumer spending or continued disruption in the availability of credit to retailers or consumers, could materially and adversely affect our business, results of operations and financial condition.

Our international business exposes us to additional risks.

Our operations outside of the U.S. are subject to risks that are inherent in conducting business under non-U.S. laws, regulations and customs, including those related to:

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foreign currency exchange rate fluctuations, potentially reducing the U.S. dollars we receive for sales denominated in foreign currency;

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the possibility that unfriendly nations or groups could boycott our solutions;

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political conditions in the markets in which we operate;

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potential increased costs associated with overlapping tax structures;

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import-export control;

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more limited protection for intellectual property rights in some countries;

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difficulties and costs associated with staffing and managing foreign operations;

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unexpected changes in regulatory requirements;

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the difficulties of compliance with a wide variety of foreign laws and regulations;

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longer accounts receivable cycles in certain foreign countries, whether due to cultural differences, exchange rate fluctuation or other factors;

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technology transfer restrictions;

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changes to our distribution networks; and

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our employees.

These risks, individually or in the aggregate, could have an adverse effect on our results of operations and financial condition. For example, we are subject to compliance with the Foreign Corrupt Practices Act and similar anti-bribery laws, which generally prohibit companies and their intermediaries from making improper payments to foreign government officials for the purpose of obtaining or retaining business. While our employees and agents are required to comply with these laws, we cannot be sure that our internal policies and procedures will always protect us from violations of these laws, despite our commitment to legal compliance and corporate ethics. The occurrence or allegation of these types of risks may adversely affect our business, performance, prospects, value, financial condition, and results of operations. In addition, our international contracts may include industrial cooperation agreements requiring specific in-country purchases, investments, manufacturing agreements or other financial obligations, known as offset obligations, and provide for penalties if we fail to meet such requirements. The impact of these factors is difficult to predict, but one or more of them could adversely affect our financial position, results of operations, or cash flows.

Violations of the International Traffic in Arms Regulations ("ITAR") or other applicable trade compliance regulations could result in significant sanctions including fines, more onerous compliance requirements and debarments from export privileges or loss of authorizations needed to conduct aspects of our international business. A violation of ITAR or other applicable trade regulations could materially adversely affect our business, financial condition and results of operations.

Risks related to our outstanding indebtedness

We have substantial indebtedness, which could adversely affect our cash flow, financial condition and business.

As of June 25, 2017, we had approximately $370.5 million of total indebtedness outstanding, which includes $1.6 million of unamortized original issue discount and $2.0 million of unamortized debt issuance costs. As a result of this indebtedness, our interest payment obligations are significant. The degree to which we are leveraged could have adverse effects on our business, including the following:

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it may limit our flexibility in planning for, or reacting to, changes in our business and the industries in which we operate;

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it may require us to dedicate a substantial portion of our cash flow from operations to payments on our indebtedness, thereby reducing the availability of our cash flow to fund working capital, capital expenditures and other general corporate purposes;

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it may restrict us from making strategic acquisitions or exploiting business opportunities;

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it may place us at a competitive disadvantage compared to our competitors that have less debt;

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it may limit our ability to borrow additional funds;

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•

it may prevent us from raising the funds necessary to repurchase our outstanding 7.00% Senior Secured Notes due in 2019 (the "Notes") tendered to us if there is a change of control, which would constitute a default under the Indenture, dated May 14, 2014 ("Indenture"), among the Company, certain of the Company's 100% owned domestic subsidiaries, and Wilmington Trust, National Association, as Trustee and Collateral Agent, governing such Notes and under our Credit Agreement; and

•

it may decrease our ability to compete effectively or operate successfully under adverse economic and industry conditions.

Our high level of indebtedness increases the risk that we may default on our debt obligations. We may be unable to generate sufficient cash flow to pay the interest on our debt. If we are unable to service our indebtedness, we will be forced to adopt an alternative strategy that may include actions such as reducing capital expenditures, reducing internal investments in research and development efforts, selling assets, restructuring or refinancing our indebtedness or seeking additional equity capital. These alternative strategies may not be affected on satisfactory terms, if at all, and they may not yield sufficient funds to make required payments on our indebtedness.

If, for any reason, we are unable to meet our debt service and repayment obligations, we would be in default under the terms of the agreements governing our debt, which would allow our creditors at that time to declare certain outstanding indebtedness to be due and payable, which would in turn trigger cross-acceleration or cross-default rights between the relevant agreements. In addition, the noteholders of the Notes could foreclose against the assets securing their Notes and we could be forced into bankruptcy or liquidation and/or our lenders could compel us to apply all of our available cash to repay our borrowings or they could prevent us from making payments on our indebtedness. If the amounts outstanding under any of our indebtedness were to be accelerated, our assets may not be sufficient to repay in full the money owed to the lenders or to our other debt holders.

We and our subsidiaries may incur more debt, which may increase the risks associated with our substantial leverage, including our ability to service our indebtedness.

The agreements governing our debt permit us, under some circumstances, to incur certain additional indebtedness or obligations. To the extent that we incur additional indebtedness or such other obligations, the risks associated with our substantial leverage described above, including our possible inability to service our debt, would increase.

Changes in our credit ratings or macroeconomic conditions may affect our liquidity, increasing borrowing costs and limiting our financing options.

Macroeconomic conditions, such as increased volatility or disruption in the credit markets, could adversely affect our ability to refinance existing debt or obtain additional financing at terms satisfactory to us, thereby affecting our resources to support operations or to fund new initiatives. In addition, if our credit ratings are lowered, borrowing costs for future long-term debt or short-term credit facilities may increase and our financing options, including our access to the unsecured credit market, could be limited. We may also be subject to restrictive covenants that would reduce our flexibility.

We may not be able to refinance our Notes on acceptable terms.

As of June 25, 2017, there was $372.8 million in outstanding Notes which mature and become due and payable on May 15, 2019. If we are unable to refinance or restructure our Notes on or before that date, we may not have sufficient capital resources to repay in full the outstanding principal amount and any interest due on the Notes, which would constitute an event of default under the terms of the Indenture governing

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the Notes and which, if not cured or waived, could result in the acceleration of substantially all of our debt. If we cannot make our scheduled debt payments, we will be in default and all outstanding principal and interest on our debt may be declared due and payable, the noteholders of the Notes could foreclose against the assets securing their Notes and we could be forced into bankruptcy or liquidation.

Our ability to refinance our Notes will depend on, among other things:

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our financial condition and operating performance at the time;

•

restrictions in agreements governing our indebtedness, including the Indenture governing the Notes and our Credit Agreement; and

•

other factors, including financial market or industry conditions, many of which are beyond our control.

Any refinancing of our Notes could be at higher interest rates and may require us to comply with more onerous covenants, which could further restrict our business operations. As a result, it may be difficult for us to obtain financing on terms that are acceptable to us, or at all.

A portion of our business is conducted through foreign subsidiaries, and the failure to generate sufficient cash flow from these subsidiaries, or otherwise repatriate or receive cash from these subsidiaries, could result in our inability to repay our indebtedness.

As of June 25, 2017, approximately 12% of our consolidated assets, based on book value, and approximately 10% of our consolidated revenues for the six months ended June 25, 2017, were held by foreign subsidiaries, which do not guarantee the Notes. Our ability to meet our debt service obligations with cash from foreign subsidiaries will depend upon the results of operations of these subsidiaries and may be subject to legal, contractual or other restrictions and other business considerations. In addition, dividend and interest payments to us from the foreign subsidiaries may be subject to foreign withholding taxes, which would reduce the amount of funds we receive from such foreign subsidiaries. Dividends and other distributions from our foreign subsidiaries may also be subject to fluctuations in currency exchange rates and legal and other restrictions on repatriation, which could further reduce the amount of funds we receive from such foreign subsidiaries.

In general, when an entity in a foreign jurisdiction repatriates cash to the U.S., the amount of such cash is treated as a dividend taxable at current U.S. tax rates. Accordingly, upon the distribution of cash to us from our foreign subsidiaries, we will be subject to U.S. income taxes. Although foreign tax credits may be available to reduce the amount of the additional tax liability, these credits may be limited and only offset the tax paid in the foreign jurisdiction, not the excess of the U.S. tax rate over the foreign tax rate. Therefore, to the extent that we must use cash generated in foreign jurisdictions to make principal or interest payments on our debt, there may be a cost associated with repatriating the cash to the U.S.

The agreements governing our debt impose significant operating and financial restrictions on us and our subsidiaries that may prevent us and our subsidiaries from pursuing certain business opportunities and restrict our ability to operate our business.

The Indenture and the Credit Agreement subject us, and our subsidiaries, to several financial and other restrictive covenants, including limitations on liens or indebtedness, payment of dividends, transactions with affiliates, and mergers, sales or other dispositions of our assets.

Our Credit Agreement also requires us to comply with specified financial ratios, including a borrowing base availability and minimum fixed charge coverage ratio which is required to be maintained if borrowing levels, as defined, under the Credit Agreement, occur under the line of credit. Many factors, including

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events beyond our control, may affect our ability to comply with these covenants and financial ratios. We cannot be sure we will meet our debt-related obligations or that lenders will waive any failure to meet those obligations. Any failure to meet those debt-related obligations could result in an event of default under our other indebtedness and the acceleration of such indebtedness.

The restrictions contained in the Indenture and in our Credit Agreement could also limit the ability of the Company and its subsidiaries to plan for or react to market conditions, meet capital needs or otherwise restrict their activities or business plans and adversely affect the ability to finance their operations, enter into acquisitions or to engage in other business activities that would be in their interest.

Risks related to our intellectual property

We may be unable to protect our intellectual property rights.

We rely on a combination of patents, trademarks, copyrights, trade secrets and nondisclosure agreements to protect our proprietary intellectual property. Our efforts to protect our intellectual property and proprietary rights may not be sufficient. We cannot be sure that our pending patent applications will result in the issuance of patents to us, that patents issued to or licensed by us in the past or in the future will not be challenged or circumvented by competitors or that these patents will remain valid or sufficiently broad to preclude our competitors from introducing technologies similar to those covered by our patents and patent applications. In addition, our ability to enforce and protect our intellectual property rights may be limited in certain countries outside the U.S., which could make it easier for competitors to capture market position in such countries by utilizing technologies that are similar to those developed or licensed by us. Competitors also may harm our sales by designing products that mirror the capabilities of our products or technology without infringing on our intellectual property rights. If we do not obtain sufficient protection for our intellectual property, or if we are unable to effectively enforce our intellectual property rights, our competitiveness could be impaired, which would limit our growth and future revenue.

We may be harmed by intellectual property infringement claims.

We may become subject to claims from our employees or third parties who assert that software and other forms of intellectual property that we use in delivering services and solutions to our customers infringe upon intellectual property rights of such employees or third parties. Our employees develop some of the software and other forms of intellectual property that we use to provide our services and solutions to our customers, but we also license technology from other vendors. If our employees, vendors, or other third parties assert claims that we or our customers are infringing on their intellectual property rights, we could incur substantial costs to defend those claims. If any such infringement claims were ultimately successful, we could be required to cease selling or using products or services that incorporate the challenged software or technology, obtain a license or additional licenses from our employees, vendors, or other third parties, or redesign our products and services that rely on the challenged software or technology.

Disclosure of trade secrets could cause harm to our business.

We attempt to protect our trade secrets by entering into confidentiality and intellectual property assignment agreements with third parties, our employees and consultants. However, these agreements can be breached and, if they are, there may not be an adequate remedy available to us. In addition, others may independently discover our trade secrets and proprietary information, and in such cases we could not assert any trade secret rights against such party. Enforcing a claim that a party illegally obtained and is using our trade secret is difficult, expensive and time consuming, and the outcome is unpredictable. If we are unable to protect our intellectual property, our competitors could market services or products similar to our services and products, which could reduce demand for our offerings. Any litigation to enforce our

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intellectual property rights, protect our trade secrets or determine the validity and scope of the proprietary rights of others could result in substantial costs and diversion of resources, with no assurance of success.

Risks related to regulatory, environmental and legal issues

Our failure to comply with complex procurement laws and regulations could cause us to lose business and subject us to a variety of penalties.

We must comply with laws and regulations relating to the formation, administration and performance of U.S. Government contracts, which affect how we do business with our customers, prime contractors, subcontractors and vendors and may impose added costs on us. New regulations or procurement requirements (including, for example regulations regarding counterfeit and corrupt parts, supply chain diligence and cyber security) or changes to current requirements could increase our costs and risk of non-compliance. Our role as a contractor to agencies and departments of the U.S. Government results in our being routinely subject to investigations and reviews relating to compliance with various laws and regulations, including those associated with organizational conflicts of interest, procurement integrity, bid integrity and claim presentation, among others. These investigations may be conducted without our knowledge. Adverse findings in these investigations or reviews can lead to criminal, civil or administrative proceedings, and we could face civil and criminal penalties and administrative sanctions, including termination of contracts, forfeiture of profits, suspension of payments, fines and suspension or debarment from doing business with U.S. Government agencies. In addition, we could suffer serious harm to our reputation and competitive position if allegations of impropriety were made against us, whether or not true. If our reputation or relationship with U.S. Government agencies were impaired, or if the U.S. Government otherwise ceased doing business with us or significantly decreased the amount of business it does with us, our revenue and operating profit would decline.

Our contracts and administrative processes and systems are subject to audits and cost adjustments by the U.S. Government, which could reduce our revenue, disrupt our business or otherwise adversely affect our results of operations.

U.S. Government agencies, including the Defense Contract Audit Agency ("DCAA"), routinely audit and investigate government contracts and government contractors' administrative processes and systems. These agencies review our performance on contracts, pricing practices, cost structure and compliance with applicable laws, regulations and standards. They also review the adequacy of our compliance with government standards for our accounting and management of internal control systems, including our: control environment and overall accounting system, general IT system, budget and planning system, purchasing system, material management and accounting system, compensation system, labor system, indirect and other direct costs system, and billing system and estimating system used for pricing on government contracts. Both contractors and the U.S. Government agencies conducting these audits and reviews have come under increased scrutiny. The current audits and reviews have become more rigorous, and the standards to which contractors are being held are being more strictly interpreted, increasing the likelihood of an audit or review resulting in an adverse outcome. During the course of its current audits, the DCAA is closely examining and questioning several of our established and disclosed practices that it had previously audited and accepted, increasing the uncertainty as to the ultimate conclusion that will be reached.

A finding of significant control deficiencies in our system audits or other reviews can result in decremented billing rates to our U.S. Government customers until the control deficiencies are corrected and our corrections are accepted by Defense Contract Management Agency. Government audits and reviews may conclude that our practices are not consistent with applicable laws and regulations and result in

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adjustments to contract costs and mandatory customer refunds. Such adjustments can be applied retroactively, which could result in significant customer refunds. Our receipt of adverse audit findings or the failure to obtain an "approved" determination of our various accounting and management internal control systems, including our changes to indirect cost and direct labor estimating systems, from the responsible U.S. Government agency could significantly and adversely affect our business, including our ability to bid on new contracts and our competitive position in the bidding process. A determination of non-compliance with applicable contracting and procurement laws, regulations and standards could also result in the U.S. Government imposing penalties and sanctions against us, including withholding of payments, suspension of payments and increased government scrutiny that could delay or adversely affect our ability to invoice and receive timely payment on contracts, perform contracts or compete for contracts with the U.S. Government.

We have submitted incurred cost claims through 2016. The actual indirect cost audits by the DCAA have been completed for all of our subsidiaries through fiscal 2010, and have been completed for certain of our subsidiaries through fiscal 2014. Although we have recorded contract revenues subsequent to such completed audits based upon costs that we believe will be approved upon final audit or review, we do not know the outcome of any ongoing or future audits or reviews and, if future adjustments exceed our estimates, our profitability would be adversely affected.

Our employees or others acting on our behalf may engage in misconduct or other improper activities, which could cause us to lose contracts.

We are exposed to the risk that employee fraud or other misconduct from our employees or others acting on our behalf could occur. Misconduct by employees or others could include intentional failures to comply with U.S. Government procurement regulations, engaging in unauthorized activities or falsifying time records. Misconduct by our employees or others acting on our behalf could also involve the improper use of our customers' sensitive or classified information, which could result in regulatory sanctions against us, serious harm to our reputation, a loss of contracts and a reduction in revenues. It is not always possible to deter misconduct, and the precautions we take to prevent and detect this activity may not be effective in controlling unknown or unmanaged risks or losses, which could cause us to lose contracts or cause a reduction in revenues. In addition, alleged or actual misconduct by employees or others acting on our behalf could result in investigations or prosecutions of persons engaged in the subject activities, which could result in unanticipated consequences or expenses and management distraction for us regardless of whether we are alleged to have any responsibility.

If we fail to maintain an effective system of internal controls, we may not be able to accurately report our financial results or prevent fraud.

Effective internal controls are necessary for us to provide reliable financial reports. If we cannot provide reliable financial reports, our operating results could be misstated, our reputation may be harmed and the trading price of our stock could be negatively affected. Although we continue to devote substantial time and resources to the documentation and testing of our controls, there can be no assurance that our controls over financial processes and reporting will be effective in the future or that material weaknesses or significant deficiencies in our internal controls will not be discovered in the future. Any failure to remediate any future material weaknesses or implement required new or improved controls, or difficulties encountered in their implementation, could harm our operating results, cause us to fail to meet our reporting obligations or result in material misstatements in our Consolidated Financial Statements or other public disclosures. Inferior internal controls could also cause investors to lose confidence in our reported financial information, which could have a negative effect on the trading price of our stock.

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We are subject to environmental laws and potential exposure to environmental liabilities. This may affect our ability to develop, sell or rent our property or to borrow money where such property is required to be used as collateral.

We use hazardous materials common to the industries in which we operate. We are required to follow federal, state and local environmental laws and regulations regarding the handling, storage and disposal of these materials, including the Clean Air Act, the Clean Water Act, the Resource Conservation and Recovery Act, the Comprehensive Environmental Response, Compensation and Liability Act ("CERCLA"), and the Toxic Substances Control Act. We could be subject to fines, suspensions of production, alteration of our manufacturing processes or interruption or cessation of our operations if we fail to comply with present or future laws or regulations related to the use, storage, handling, discharge or disposal of toxic, volatile or otherwise hazardous chemicals used in our manufacturing processes. These regulations could require us to acquire expensive remediation equipment or to incur significant other expenses to comply with environmental regulations. Our failure to control the handling, use, storage or disposal of, or adequately restrict the discharge of, hazardous substances could subject us to liabilities and production delays, which could cause us to miss our customers' delivery schedules, thereby reducing our sales for a given period. We may also have to pay regulatory fines, penalties or other costs (including remediation costs), which could materially reduce our profits and adversely affect our financial condition. Permits are required for our operations, and these permits are subject to renewal, modification and, in some cases, revocation.

In addition, under environmental laws, ordinances or regulations, a current or previous owner or operator of property may be liable for the costs of removal or remediation of some kinds of petroleum products or other hazardous substances on, under, or in its property, adjacent or nearby property, or offsite disposal locations, without regard to whether the owner or operator knew of, or caused, the presence of the contaminants, and regardless of whether the practices that resulted in the contamination were legal at the time they occurred. We have incurred, and may incur in the future, liabilities under CERCLA and other environmental laws at our current or former facilities, adjacent or nearby properties or offsite disposal locations. The costs associated with future cleanup activities that we may be required to conduct or finance may be material. The presence of, or failure to remediate properly, hazardous substances may adversely affect the ability to sell or rent the property or to borrow funds using the property as collateral. Additionally, we may become subject to claims by third parties based on damages, including personal injury and property damage, and costs resulting from the disposal or release of hazardous substances into the environment.

Regulations related to "conflict minerals" may cause us to incur additional expenses and could limit the supply and increase the cost of certain metals used in manufacturing our products.

We are subject to regulations requiring disclosures of specified minerals, known as conflict minerals, that are necessary to the functionality or production of products manufactured or contracted to be manufactured by public companies. The rule requires companies to perform due diligence, disclose and report whether or not such minerals originate from the Democratic Republic of the Congo or an adjoining country. The rule can affect sourcing at competitive prices and availability in sufficient quantities of certain minerals used in the manufacture of our products, including tantalum, tin, gold and tungsten. The number of suppliers who provide conflict-free minerals is limited. In addition, there are costs associated with complying with the disclosure requirements, such as costs related to determining the source of certain minerals used in our products, as well as costs of changes to products, processes, or sources of supply as a consequence of such verification activities. Since our supply chain is complex, we are not always able to sufficiently verify the origins of the relevant minerals used in our products through the due diligence procedures we implemented, which may harm our reputation. In addition, we may encounter challenges to

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satisfy those customers who require that all of the components of our products be certified as conflict-free, which could place us at a competitive disadvantage if we are unable to do so.

Litigation may distract us from operating our business, and adverse judgments or settlements could adversely affect our financial results and operations.

Litigation that may be brought by or against us could cause us to incur significant expenditures and distract our management from the operation of our business. Furthermore, there can be no assurance that we would prevail in such litigation or resolve such litigation on terms favorable to us, which may adversely affect our financial results and operations. See Note 14 of the Notes to Consolidated Financial Statements contained within our Annual Report on Form 10-K for the fiscal year ended December 25, 2016 and Note 10 of the Notes to Condensed Consolidated Financial Statements (unaudited) contained within our Quarterly Report on Form 10-Q for the quarterly period ended June 25, 2017, which are incorporated herein by reference, for a further discussion of our legal proceedings.

Natural disasters or severe weather conditions could disrupt our business and result in loss of revenue or higher expenses.

Our business depends on maintaining operations at our facilities and being able to operate at our customer facilities and project locations. A serious, prolonged interruption or damage due to power outage, telecommunications outage, terrorist attack, earthquake, hurricane, fire, flood or other natural disaster, or other interruption could have a material adverse effect on our business and financial results. While we insure against certain business interruption risks, such insurance may not adequately compensate us for any losses incurred as a result of natural or other disasters.

Risks related to our common stock

Some of our contracts with the U.S. Government are classified, which may limit investor insight into portions of our business.

We derive a portion of our revenues from programs with the U.S. Government that are subject to security restrictions (classified programs) that preclude the dissemination of information that is classified for national security purposes. We are limited in our ability to provide details about these classified programs, their risks or any disputes or claims relating to such programs. As a result, investors and others might have less insight into our classified programs than our other businesses and, therefore, less ability to fully evaluate the risks related to our classified business.

The market price of our common stock may be volatile.

The price of our stock has been in the past, and will continue to be, subject to fluctuations as a result of a number of factors, including: our operating results fail to meet market or analysts' expectations; general fluctuations in the stock market; actual or anticipated fluctuations in our operating results based on reduced and/or delayed government spending or the threat thereof; fluctuations in the stock prices of companies in our industry; changes in earnings estimated by securities analysts or our ability to meet those estimates; and domestic and foreign economic conditions. Such volatility has had a significant effect on the market prices of many companies' securities for reasons unrelated to their operating performance and, in the past, has led to securities class action litigation. Securities litigation against us could result in substantial costs and a diversion of our management's attention and resources, which could have an adverse effect on our business.

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Your percentage of ownership in us may be diluted in the future.

As with any publicly traded company, your percentage ownership in us may be diluted in the future because of equity issuances for acquisitions, capital market transactions or otherwise, including equity awards that we expect will be granted to our directors, officers and employees.

Certain provisions in our amended and restated certificate of incorporation and second amended and restated bylaws, as amended, and of Delaware law, may prevent or delay an acquisition of our Company, which could decrease the trading price of our common stock.

Our amended and restated certificate of incorporation, our second amended and restated bylaws, as amended, and Delaware law contain provisions that are intended to deter coercive takeover practices and inadequate takeover bids by making such practices or bids unacceptably expensive to the raider and to encourage prospective acquirers to negotiate with our board of directors rather than to attempt a hostile takeover. These provisions include, among others:

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the inability of our stockholders to call a special meeting;

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rules regarding how stockholders may present proposals or nominate directors for election at stockholder meetings;

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the right of our board of directors to issue preferred stock without stockholder approval;

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a super-majority requirement to amend our certificate of incorporation or bylaws; and

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the ability of our directors, and not stockholders, to fill vacancies on our board of directors.

Delaware law also imposes some restrictions on mergers and other business combinations between us and any holder of 15% or more of our outstanding common stock.

We believe these provisions may help protect our stockholders from coercive or otherwise unfair takeover tactics by requiring potential acquirers to negotiate with our board of directors and by providing our board of directors with more time to assess any acquisition proposal. These provisions are not intended to make our Company immune from takeovers. In addition, although we believe these provisions collectively provide for an opportunity to receive higher bids by requiring potential acquirers to negotiate with our board of directors, they would apply even if the offer may be considered beneficial by some stockholders. These provisions may also frustrate or prevent any attempts by our stockholders to replace or remove our current management team by making it more difficult for stockholders to replace members of our board of directors, which is responsible for appointing the members of our management.

Risks related to investments in our securities

We may allocate the net proceeds from this offering in ways that you and other stockholders may not approve.

We expect to use the net proceeds from this offering to position the Company for projected growth from new and anticipated increased production on under contract programs and expected to be received new programs and contracts, to reduce our indebtedness in order to reduce our cost of capital and facilitate our long-term strategy, and for general corporate purposes, including potential acquisitions. In general, our management will have broad discretion in the application of the net proceeds from this offering and could spend the net proceeds in ways that do not necessarily improve our operating results or enhance the value of our common stock.

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You will incur immediate and substantial dilution in the net tangible book value of the shares you purchase in this offering.

The price at which we are offering shares of our common stock in this offering is higher than the net tangible book deficit per share of outstanding common stock prior to completion of the offering. Based on our net tangible book deficit as of June 25, 2017 and upon the issuance and sale of 12,500,000 shares of common stock by us (which assumes the underwriters do not exercise their option to purchase additional shares), you will suffer immediate dilution of approximately $              per share in net tangible book value. Dilution is the amount by which the offering price paid by purchasers of our common stock in this offering will exceed the as adjusted net tangible book value per share of our common stock upon completion of this offering. If the underwriters exercise their option to purchase additional shares, or if outstanding options to purchase our common stock are exercised, you will experience additional dilution. You may experience additional dilution upon future equity issuances or the exercise of stock options to purchase common stock granted to our employees, executive officers and directors under our equity incentive plan or our employee stock purchase plan. See "Dilution."

Our stock price may be volatile, and your investment in our stock could suffer a decline in value.

The market price of our common stock may fluctuate significantly, and you may not be able to resell your shares at or above the price at which you purchased your shares. Factors which could have a significant impact on the market price of our common stock include, but are not limited to, the following, most of which we cannot control:

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quarterly variations in operating results;

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changes in preference by our customers;

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announcements of new services or products or significant price reductions by us or our competitors or other actions by our competitors;

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the gain or loss of significant customers;

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stock price performance or changes in the market valuations of our competitors;

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changes in analysts' earnings estimates or publication of research reports about our industry;

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rumors or dissemination of false information;

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default on our indebtedness;

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changes in our senior management or key personnel;

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pricing pressures;

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fluctuations in stock market prices and volumes;

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short selling of our common stock;

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litigation and government inquiries;

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general conditions in the market;

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political and/or military events associated with current worldwide conflicts; and

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events affecting other companies that investors deem comparable to us.

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These and other external factors may cause the market price and demand for our common stock to fluctuate substantially, which may limit or prevent investors from readily selling their shares of common stock and may otherwise negatively affect the liquidity of our common stock. Volatility in the market price of our common stock could also subject us to securities class action litigation.

Future sales of our common stock could cause the market price for our common stock to decline.

We cannot predict the effect, if any, that market sales of shares of our common stock or the availability of shares of our common stock for sale will have on the market price of our common stock prevailing from time to time. Sales of substantial amounts of shares of our common stock in the public market, or the perception that those sales will occur, could cause the market price of our common stock to decline or be depressed.

The shares of common stock issued in connection with this offering will be freely tradable without restriction or further registration under the Securities Act of 1933, as amended (the "Securities Act").

In connection with his offering, we and our directors and executive officers have agreed with the underwriters to a "lock-up", pursuant to which neither we nor they will sell, hedge or otherwise dispose of any shares without the prior written consent of J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC for 90 days after the date of this prospectus supplement, subject to certain exceptions. Following the expiration of the applicable lock-up period, all these shares of our common stock will also be eligible for future sale.

In the future, we may also issue our securities if we need to raise capital in connection with a capital expenditure or acquisition. The amount of shares of our common stock issued in connection with a capital expenditure or acquisition could constitute a material portion of our then-outstanding shares of common stock. Any perceived excess in the supply of our shares in the market could negatively impact our share price and any issuance of additional securities in connection with investments or acquisitions may result in additional dilution to you.

We do not expect to pay any cash dividends for the foreseeable future.

We have not declared any cash dividends since becoming a public company. We currently intend to retain any future earnings to finance the growth and development of the business and, therefore, we do not anticipate that we will pay any cash dividends on shares of our common stock in the foreseeable future. In addition, our ability to pay dividends is restricted by both the Indenture and the Credit Agreement. Any determination to pay dividends in the future will be at the discretion of our board of directors and will be dependent upon our future financial condition, results of operations and capital requirements, general business conditions and other relevant factors as determined by our board of directors. Accordingly, if you purchase shares in this offering, realization of a gain on your investment will depend on the appreciation of the price of our common stock, which may never occur. Investors seeking cash dividends in the foreseeable future should not purchase our common stock. See "Dividend policy."

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Cautionary note regarding forward-looking statements

This prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein contain forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended (the "Exchange Act") and the Private Securities Litigation Reform Act of 1995. These statements involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed in or implied by the forward-looking statements. Forward-looking statements may include, but are not limited to, statements relating to our future financial performance, the growth of the market for our services, expansion plans and opportunities and statements regarding our intended uses of the proceeds of the securities offered hereby. In some cases, you can identify forward-looking statements by terminology such as "may," "will," "should," "expect," "plan," "anticipate," "believe," "estimate," "predict," "potential" or "continue," the negative of such terms or other comparable terminology.

The forward-looking statements contained in this prospectus supplement reflect our current views about future events, are based on assumptions, and are subject to known and unknown risks and uncertainties. Many important factors could cause actual results or achievements to differ materially from any future results or achievements expressed in or implied by our forward-looking statements, including the factors listed below. Many of the factors that will determine future events or achievements are beyond our ability to control or predict. Certain of these are important factors that could cause actual results or achievements to differ materially from the results or achievements reflected in our forward-looking statements, including, but not limited to:

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risks to our business and financial results related to the reductions and other spending constraints imposed on the U.S. Government and our other customers, including as a result of sequestration, the federal budget deficit and federal government shut-downs; risks of adverse regulatory action or litigation;

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risks associated with debt leverage and expected cost savings and cash flow improvements expected as a result of the refinancing of our Notes and the repurchase of Notes;

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risks that our cost-cutting initiatives will not provide the anticipated benefits;

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risks that changes, cutbacks or delays in spending by the DoD may occur, which could cause delays or cancellations of key government contracts;

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risks of delays to or the cancellation of our projects as a result of protest actions submitted by our competitors;

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risks that changes may occur in federal government (or other applicable) procurement laws, regulations, policies and budgets;

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risks of the availability of government funding for the Company's products and services due to performance, cost growth, or other factors, changes in government and customer priorities and requirements (including cost-cutting initiatives, the potential deferral of awards, terminations or reduction of expenditures to respond to the priorities of Congress and the Administration, or budgetary cuts resulting from Congressional committee recommendations or automatic sequestration under the Budget Control Act);

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risks of increases in the federal government initiatives related to in-sourcing;

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risks related to security breaches, including cybersecurity attacks and threats or other significant disruptions of our information systems, facilities and infrastructures;

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risks related to our compliance with applicable contracting and procurement laws, regulations and standards;

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risks relating to contract performance; risks related to failure of our products or services;

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risks associated with our subcontractors' or suppliers' failure to perform their contractual obligations, including the appearance of counterfeit or corrupt parts in our products;

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changes in the competitive environment (including as a result of bid protests); failure to successfully integrate acquired operations and competition in the marketplace, which could reduce revenues and profit margins;

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risks that potential future goodwill impairments will adversely affect our operating results;

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risks that anticipated tax benefits will not be realized in accordance with our expectations; risks that a change in ownership of our stock could cause further limitation to the future utilization of our net operating losses; and

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risks that the current economic environment will adversely impact our business; and risks related to natural disasters or severe weather.

The forward-looking statements contained in this prospectus supplement reflect our views and assumptions only as of the date of this prospectus supplement. You should not place undue reliance on forward-looking statements. Except as required by law, we assume no responsibility for updating any forward-looking statements nor do we intend to do so. Our actual results, performance or achievements could differ materially from the results expressed in, or implied by, these forward-looking statements. The risks included in this section are not exhaustive. There may be other factors that could cause actual results to differ materially from those described in the forward-looking statements, including those described in the sections entitled "Risk factors" beginning on page S-13 and "Management's Discussion and Analysis of Financial Condition and Results of Operations" appearing in Item 7 of our Annual Report on Form 10-K for the fiscal year ended December 25, 2016, incorporated herein by reference.

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Use of proceeds

We expect the net proceeds from this offering to be approximately $               million (or $               million if the underwriters exercise their option to purchase additional shares in full), after deducting underwriting discounts and commissions, as described in "Underwriting," and estimated offering expenses payable by us. We expect to use the net proceeds from this offering to position the Company for projected growth from new and anticipated increased production on under contract programs and expected to be received new programs and contracts, to reduce our indebtedness in order to reduce our cost of capital and facilitate our long-term strategy, and for general corporate purposes, including potential acquisitions.

The Company's outstanding indebtedness includes the Notes, which mature in 2019 and bear interest at 7.00%. As of June 25, 2017, there was $372.8 million in Notes outstanding.

Our board of directors has approved the use of up to the full amount of the net proceeds from this offering to repurchase, from time to time, our outstanding Notes, subject to compliance with applicable laws and existing covenant restrictions under the Credit Agreement.

As of the date of this prospectus supplement, we cannot specify with certainty all of the particular uses of the proceeds from this offering. Accordingly, we will retain broad discretion over the use of such proceeds. Pending the use of the net proceeds from this offering as described above, we intend to invest the net proceeds in short-term, investment-grade securities.

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Capitalization

The following table sets forth our cash and cash equivalents and capitalization as of June 25, 2017:

•

on an actual basis; and

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as adjusted to give effect to the receipt of estimated net proceeds of $              from this offering at an offering price of $              per share of common stock after deducting estimated underwriting discounts and estimated offering expenses payable by us, and the application of the net proceeds therefrom as described above under the heading "Use of proceeds."

The following table should be read in conjunction with our consolidated financial statements and related notes, which are incorporated by reference into this prospectus supplement (unaudited):

The number of shares of our common stock to be outstanding immediately after the closing of this offering is based on 86,634,053 shares of common stock outstanding as of June 25, 2017 and excludes, as of that date:

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899,618 shares of common stock issuable upon the exercise of outstanding stock options at a weighted average exercise price of $7.83 per share;

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5,483,467 shares of common stock available for future grant under the Plans; and

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2,987,650 shares of common stock issuable upon the vesting and settlement of restricted stock units.

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Dilution

If you purchase shares in this offering, your interest will be diluted to the extent of the difference between the offering price per share and the as adjusted net tangible book value per share of our common stock after this offering. Dilution results from the fact that the per share offering price of the common stock is substantially in excess of the book value per share attributable to the already outstanding shares of common stock held by existing stockholders. Our net tangible book deficit as of June 25, 2017 was $(165.7) million, or $(1.91) per share of common stock. "Net tangible book value (deficit)" is total assets minus the sum of liabilities and intangible assets. "Net tangible book value (deficit) per share" is net tangible book value (deficit) divided by the total number of shares of common stock outstanding.

After giving effect to the sale by us of 12,500,000 shares of our common stock (which assumes the underwriters do not exercise their option to purchase additional shares) in this offering at the offering price of $              per share, and after deducting underwriting discounts and commissions, and approximately $              of estimated offering expenses payable by us, our as adjusted net tangible book deficit as of June 25, 2017 would have been approximately $(              ) million, or $ (              ) per share of common stock. This amount represents an immediate decrease in net tangible book deficit of $              per share to existing stockholders and an immediate dilution of $              per share to purchasers in this offering.

The following table illustrates the dilution:

The number of shares of our common stock to be outstanding immediately after the closing of this offering is based on 86,634,053 shares of common stock outstanding as of June 25, 2017 and excludes, as of that date:

•

899,618 shares of common stock issuable upon the exercise of outstanding stock options at a weighted average exercise price of $7.83 per share;

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5,483,467 shares of common stock available for future grant under the Plans; and

•

2,987,650 shares of common stock issuable upon the vesting and settlement of restricted stock units.

If the underwriters exercise in full their option to purchase additional shares of common stock, our as adjusted net tangible book deficit as of June 25, 2017 would have been approximately $(              ) million, or $(              ) per share of common stock, representing an immediate decrease in net tangible book deficit of $              per share to existing stockholders and an immediate dilution of $              per share to purchasers in this offering.

To the extent that any outstanding options are exercised, new options are issued under the Plans, or we otherwise issue additional shares of common stock in the future, at a price less than the public offering price, there will be further dilution to the investors.

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Price range of common stock

Our common stock trades on the NASDAQ Global Select Market ("NASDAQ") under the symbol "KTOS." As of June 25, 2017, there were 384 holders of record of our common stock. This stockholder figure does not include a substantially greater number of holders whose shares are held of record by banks, brokers and other financial institutions. The following table sets forth the high and low sale prices per share for our common stock as reported on NASDAQ for the period indicated:

The closing sale price of our common stock, as reported by NASDAQ, on September 1, 2017 was $13.39.

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Dividend policy

We have not declared any cash dividends since becoming a public company. We currently intend to retain any future earnings to finance the growth and development of the business and, therefore, do not anticipate paying any cash dividends in the foreseeable future. In addition, our ability to pay dividends is restricted by both the Indenture and the Credit Agreement. See "Risk factors—Risks related to investments in our securities—We do not expect to pay any cash dividends for the foreseeable future", "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources" and Note 4 of the Notes to Consolidated Financial Statements contained within our Annual Report on Form 10-K for the fiscal year ended December 25, 2016, incorporated herein by reference. Any future determination to pay cash dividends will be at the discretion of our board of directors and will be dependent upon our future financial condition, results of operations and capital requirements, general business conditions and other relevant factors as determined by our board of directors. We did not declare or pay dividends to the holders of our common stock in our last three fiscal years.

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Material United States federal income tax considerations for non-U.S. holders

The following is a summary of the material U.S. federal income tax considerations relevant to the purchase, ownership and disposition of our common stock by a non-U.S. holder (as defined below) as of the date hereof. This summary deals only with non-U.S. holders that acquire our common stock in this offering and hold the common stock as a capital asset within the meaning of Section 1221 of the Internal Revenue Code of 1986, as amended (the "Code") (generally, property held for investment).

For purposes of this summary, a "non-U.S. holder" means a beneficial owner of our common stock (other than an entity or arrangement treated as a partnership for U.S. federal income tax purposes) that is not any of the following for U.S. federal income tax purposes: (i) an individual citizen or resident of the U.S.; (ii) a corporation (or other entity treated as a corporation) created or organized in or under the laws of the U.S., any state thereof, or the District of Columbia; (iii) an estate the income of which is subject to U.S. federal income taxation regardless of its source; or (iv) a trust if (1) its administration is subject to the primary supervision of a court within the U.S. and one or more U.S. persons have the authority to control all of its substantial decisions, or (2) it has a valid election in effect under applicable U.S. Treasury regulations to be treated as a U.S. person.

This summary is based upon provisions of the Code and regulations, rulings and judicial decisions as of the date hereof. Those authorities may be changed, perhaps retroactively, or be subject to differing interpretations, so as to result in U.S. federal income tax considerations different from those summarized below. This summary does not represent a detailed description of the U.S. federal income tax considerations to you in light of your particular circumstances. In addition, it does not address the U.S. federal income tax considerations to you if you are subject to special treatment under the U.S. federal income tax laws (including if you are a bank or other financial institution, insurance company, broker or dealer in securities, tax-exempt organization, foreign government or agency, U.S. expatriate, "controlled foreign corporation," "passive foreign investment company," or a person who holds our common stock in a straddle or as part of a hedging, conversion or constructive sale transaction). Except where noted, this summary does not address any non-income federal tax consequences, such as estate or gift tax consequences, nor does it address any state, local, or non-U.S. tax considerations. We cannot assure you that a change in law will not alter significantly the tax considerations that we describe in this summary.

If an entity or arrangement classified as a partnership for U.S. federal income tax purposes holds our common stock, the tax treatment of a partner will generally depend on the status of the partner and the activities of the partnership. If you are a partnership holding our common stock, or a partner in such a partnership, you should consult your tax advisors.

If you are considering the purchase of our common stock, you should consult your own tax advisors concerning the particular U.S. federal tax consequences to you of the purchase, ownership and disposition of the common stock, as well as the consequences to you arising under the laws of any other taxing jurisdiction, including any state, local or foreign tax consequences.

Dividends

We have not declared any cash dividends since becoming a public company and do not anticipate paying any cash dividends on our common stock in the foreseeable future. If we were to pay cash dividends in the future on our common stock, they would be subject to U.S. federal income tax in the manner described below.

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Distributions on our common stock generally will constitute dividends for U.S. federal income tax purposes to the extent paid out of our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Distributions in excess of current and accumulated earnings and profits will be applied against and reduce a non-U.S. holder's tax basis in our common stock, to the extent thereof, and any excess will be treated as capital gain realized on the sale or other disposition of the common stock and subject to tax in the manner described below under "—Gain on disposition of common stock."

Distributions paid to a non-U.S. holder of our common stock that constitute dividends under the rules described above generally will be subject to withholding of U.S. federal income tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty. However, dividends that are effectively connected with the conduct of a trade or business by a non-U.S. holder within the U.S. and, where an income tax treaty applies, are attributable to a U.S. permanent establishment of the non-U.S. holder, are not subject to this withholding tax, but instead are subject to U.S. federal income tax on a net income basis at applicable individual or corporate rates. Certain certification and disclosure requirements must be complied with in order for effectively connected dividends to be exempt from this withholding tax. Any such effectively connected dividends received by a foreign corporation may be subject to an additional "branch profits tax" at a 30% rate or such lower rate as may be specified by an applicable income tax treaty.

A non-U.S. holder of our common stock who is entitled to and wishes to claim the benefits of an applicable treaty rate (and avoid backup withholding as discussed below) with respect to dividends received on our common stock, generally will be required to (i) complete Internal Revenue Service ("IRS") Form W-8BEN or W-8BEN-E (or an acceptable substitute form) and make certain certifications, under penalty of perjury, to establish its status as a non-U.S. person and its entitlement to treaty benefits or (ii) if the common stock is held through certain foreign intermediaries, satisfy the relevant certification requirements of applicable U.S. Treasury regulations. Special certification and other requirements apply to certain non-U.S. holders that are entities rather than individuals.

A non-U.S. holder of our common stock eligible for a reduced rate of U.S. federal withholding tax pursuant to an income tax treaty may obtain a refund of any excess amounts withheld by timely filing an appropriate claim for refund with the IRS.

Gain on disposition of common stock

Subject to the discussions below on backup withholding and the Foreign Account Tax Compliance Act, or "FATCA", a non-U.S. holder generally will not be subject to U.S. federal income tax with respect to gain recognized on a sale or other disposition of our common stock unless (i) the gain is effectively connected with a trade or business of the non-U.S. holder in the U.S. and, where a tax treaty applies, is attributable to a U.S. permanent establishment of the non-U.S. holder, (ii) in the case of a non-U.S. holder who is an individual, such holder is present in the U.S. for 183 or more days in the taxable year of the sale or other disposition and certain other conditions are met, or (iii) subject to certain exceptions, we are or have been a "U.S. real property holding corporation" for U.S. federal income tax purposes.

In the case of a non-U.S. holder described in subsection (i) above, any net gain derived from the disposition generally will be subject to U.S. federal income tax under graduated U.S. federal income tax rates in generally the same manner as if the non-U.S. holder were a U.S. person as defined under the Code, unless an applicable income tax treaty provides otherwise. Additionally, a non-U.S. holder that is a corporation may be subject to a branch profits tax equal to 30% of its effectively connected earnings and profits attributable to such gain (or, if an income tax treaty applies, at such lower rate as may be specified

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by the treaty on its gains attributable to its U.S. permanent establishment), subject to adjustments. Except as otherwise provided by an applicable income tax treaty, an individual non-U.S. holder described in subsection (ii) above will be subject to a 30% tax on any gain derived from the disposition, which may be offset by certain U.S. source capital losses. With respect to subsection (iii) above, we believe we have not been and are not currently, and do not anticipate becoming, a "U.S. real property holding corporation" for U.S. federal income tax purposes.

Information reporting and backup withholding

Payors must report annually to the IRS and to each non-U.S. holder the amount of dividends paid to such holder and the tax withheld (if any) with respect to such dividends, regardless of whether withholding was required. Copies of the information returns reporting such dividends and any withholding may also be made available to the tax authorities in the country in which the non-U.S. holder resides under the provisions of an applicable income tax treaty. In addition, dividends paid to a non-U.S. holder may be subject to backup withholding unless applicable certification requirements are met.

Payment of the proceeds of a sale of our common stock within the U.S. or conducted through certain U.S. related financial intermediaries is subject to information reporting and, depending upon the circumstances, backup withholding unless the non-U.S. holder certifies under penalties of perjury that it is not a U.S. person (and the payor does not have actual knowledge or reason to know that the holder is a U.S. person) or the holder otherwise establishes an exemption.

Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against such holder's U.S. federal income tax liability provided the required information is timely furnished to the IRS.

Foreign account tax compliance act

Legislation commonly referred to as FATCA will generally impose a 30% U.S. federal withholding tax on any "withholdable payment" (as defined below) paid to (i) a "foreign financial institution" (as specifically defined in the legislation), whether such foreign financial institution is the beneficial owner or an intermediary, unless such foreign financial institution agrees to verify, report and disclose its U.S. "account" holders (as specifically defined in the legislation) and meets certain other specified requirements, or (ii) a non-financial foreign entity, whether such non-financial foreign entity is the beneficial owner or an intermediary, unless such entity provides a certification that the beneficial owner of the payment does not have any substantial U.S. owners or provides the name, address and taxpayer identification number of each such substantial U.S. owner and certain other specified requirements are met. An intergovernmental agreement between the United States and an applicable foreign country may modify the FATCA requirements. In addition, in certain cases, the relevant foreign financial institution or non-financial foreign entity may qualify for an exemption from, or be deemed to be in compliance with, these rules. Under final regulations and other current guidance, "withholdable payments" generally include dividends on shares of common stock, and will include the gross proceeds of a disposition of shares of common stock on or after January 1, 2019. Investors are urged to consult with their own tax advisors regarding the possible application of these rules to their investment in our common stock.

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Certain ERISA considerations

The following is a summary of certain considerations associated with the purchase of our common stock by employee benefit plans that are subject to Title I of ERISA, plans, individual retirement accounts and other arrangements that are subject to Section 4975 of the Code or provisions under any federal, state, local, non-U.S. or other laws or regulations that are similar to such provisions of ERISA or the Code (collectively, "Similar Laws"), and entities whose underlying assets are considered to include "plan assets" of any such plan, account or arrangement (each, a "Plan").

General fiduciary matters

ERISA and the Code impose certain duties on persons who are fiduciaries of a Plan subject to Title I of ERISA or Section 4975 of the Code (an "ERISA Plan") and prohibit certain transactions involving the assets of an ERISA Plan and its fiduciaries or other interested parties. Under ERISA and the Code, any person who exercises any discretionary authority or control over the administration of such an ERISA Plan or the management or disposition of the assets of such an ERISA Plan, or who renders investment advice for a fee or other compensation to such an ERISA Plan, is generally considered to be a fiduciary of the ERISA Plan.

In considering an investment in our common stock of a portion of the assets of any Plan, a fiduciary should determine whether the investment is in accordance with the documents and instruments governing the Plan and the applicable provisions of ERISA, the Code or any Similar Law relating to a fiduciary's duties to the Plan including, without limitation, the prudence, diversification, delegation of control and prohibited transaction provisions of ERISA, the Code and any other applicable Similar Laws.

Prohibited transaction issues

Section 406 of ERISA and Section 4975 of the Code prohibit ERISA Plans from engaging in specified transactions involving plan assets with persons or entities who are "parties in interest," within the meaning of ERISA, or "disqualified persons," within the meaning of Section 4975 of the Code, unless an exemption is available. A party in interest or disqualified person who engaged in a non-exempt prohibited transaction may be subject to excise taxes and other penalties and liabilities under ERISA and the Code. In addition, the fiduciary of the ERISA Plan that engaged in such a non-exempt prohibited transaction may be subject to penalties and liabilities under ERISA and the Code. The acquisition and/or holding of our common stock by an ERISA Plan with respect to which we or the underwriters is considered a party in interest or a disqualified person may constitute or result in a direct or indirect prohibited transaction under Section 406 of ERISA and/or Section 4975 of the Code, unless the investment is acquired and is held in accordance with an applicable statutory, class or individual prohibited transaction exemption. In this regard, the U.S. Department of Labor has issued prohibited transaction class exemptions, or "PTCEs," that may apply to the acquisition and holding of our common stock. These class exemptions include, without limitation, PTCE 84-14 respecting transactions determined by independent qualified professional asset managers, PTCE 90-1 respecting insurance company pooled separate accounts, PTCE 91-38 respecting bank collective investment funds, PTCE 95-60 respecting life insurance company general accounts and PTCE 96-23 respecting transactions determined by in-house asset managers, although there can be no assurance that all of the conditions of any such exemptions will be satisfied.

Because of the foregoing, our common stock should not be purchased or held by any person investing "plan assets" of any Plan, unless such purchase and holding will not constitute a non-exempt prohibited transaction under ERISA and the Code or similar violation of any applicable Similar Laws.

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Representation

Accordingly, by acceptance of our common stock, each purchaser and subsequent transferee of our common stock will be deemed to have represented and warranted that either (i) no portion of the assets used by such purchaser or transferee to acquire and hold our common stock constitutes assets of any Plan or (ii) the purchase and holding of our common stock by such purchaser or transferee will not constitute a non-exempt prohibited transaction under Section 406 of ERISA or Section 4975 of the Code or similar violation under any applicable Similar Laws.

Additionally, if any purchaser or subsequent transferee of our common stock is using assets of any ERISA Plan to acquire or hold our common stock, such purchaser and subsequent transferee will be deemed to represent that (i) none of us, the underwriters, and any of our or their respective affiliates has acted as the ERISA Plan's fiduciary, or has been relied upon for any advice, with respect to the purchaser or transferee's decision to acquire, hold, sell, exchange, vote or provide any consent with respect to our common stock and none of us, the underwriters, and any of our or their respective affiliates shall at any time be relied upon as the ERISA Plan's fiduciary with respect to any decision to acquire, continue to hold, sell, exchange, vote or provide any consent with respect to our common stock and (ii) the decision to invest in our common stock has been made at the recommendation or direction of an "independent fiduciary" ("Independent Fiduciary") within the meaning of U.S. Code of Federal Regulations 29 C.F.R. Section 2510.3-21(c), as amended from time to time (the "Fiduciary Rule"), who (a) is independent of us and the underwriters; (b) is capable of evaluating investment risks independently, both in general and with respect to particular transactions and investment strategies (within the meaning of the Fiduciary Rule); (c) is a fiduciary (under ERISA and/or Section 4975 of the Code) with respect to the purchaser or transferee's investment in our common stock and is responsible for exercising independent judgment in evaluating the investment in our common stock; (d) is either (A) a bank as defined in Section 202 of the Investment Advisers Act of 1940, as amended (the "Advisers Act"), or similar institution that is regulated and supervised and subject to periodic examination by a state or federal agency of the United States; (B) an insurance carrier which is qualified under the laws of more than one state of the United States to perform the services of managing, acquiring or disposing of assets of such an ERISA Plan; (C) an investment adviser registered under the Advisers Act or, if not registered as an investment adviser under the Advisers Act by reason of paragraph (1) of Section 203A of the Advisers Act, is registered as an investment adviser under the laws of the state (referred to in such paragraph (1)) in which it maintains its principal office and place of business; (D) a broker dealer registered under the Securities Exchange Act; and/or (E) an Independent Fiduciary (not described in clauses (A), (B), (C) or (D) above) that holds or has under management or control total assets of at least $50 million, and will at all times that such purchaser or transferee holds our common stock hold or have under management or control total assets of at least $50 million; and (e) is aware of and acknowledges that (I) none of us, the underwriters and any of our or their respective affiliates is undertaking to provide impartial investment advice, or to give advice in a fiduciary capacity, in connection with the purchaser's or transferee's investment in our common stock, and (II) we, the underwriters and our and their respective affiliates have a financial interest in the purchaser's or transferee's investment in our common stock on account of the fees and other remuneration we or they expect to receive in connection with transactions contemplated hereunder. Notwithstanding the foregoing, any ERISA Plan which is an individual retirement account that is not represented by an Independent Fiduciary shall not be deemed to have made the representation in clause (ii)(d) above.

The foregoing discussion is general in nature and is not intended to be all inclusive. Due to the complexity of these rules and the penalties that may be imposed upon persons involved in non-exempt prohibited transactions, it is particularly important that fiduciaries, or other persons considering purchasing our common stock on behalf of, or with the assets of, any Plan, consult with their counsel regarding the potential applicability of ERISA, Section 4975 of the Code and any Similar Laws to such investment and whether an exemption would be applicable to the purchase and holding of our common stock.

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Underwriting

We are offering the shares of common stock described in this prospectus through a number of underwriters. J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC are acting as joint book-running managers of the offering and as representatives of the underwriters. We have entered into an underwriting agreement with the underwriters. Subject to the terms and conditions of the underwriting agreement, we have agreed to sell to the underwriters, and each underwriter has severally agreed to purchase, at the public offering price less the underwriting discounts and commissions set forth on the cover page of this prospectus, the number of shares of common stock listed next to its name in the following table:

The underwriters are committed to purchase all the common shares offered by us if they purchase any shares. The underwriting agreement also provides that if an underwriter defaults, the purchase commitments of non-defaulting underwriters may also be increased or the offering may be terminated.

The underwriters propose to offer the common shares directly to the public at the initial public offering price set forth on the cover page of this prospectus and to certain dealers at that price less a concession not in excess of $              per share. Any such dealers may resell shares to certain other brokers or dealers at a discount of up to $              per share from the initial public offering price. After the initial public offering of the shares, the offering price and other selling terms may be changed by the underwriters.

The underwriters have an option to buy up to 1,875,000 additional shares of common stock from us to cover sales of shares by the underwriters which exceed the number of shares specified in the table above. The underwriters have 30 days from the date of this prospectus to exercise this option to purchase additional shares. If any shares are purchased with this option, the underwriters will purchase shares in approximately the same proportion as shown in the table above. If any additional shares of common stock are purchased, the underwriters will offer the additional shares on the same terms as those on which the shares are being offered.

The underwriting fee is equal to the public offering price per share of common stock less the amount paid by the underwriters to us per share of common stock. The underwriting fee is $               per share. The following table shows the per share and total underwriting discounts and commissions to be paid to the underwriters assuming both no exercise and full exercise of the underwriters' option to purchase additional shares.

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We have also agreed to reimburse the underwriters for certain reasonable out-of-pocket expenses, including up to $7,550 in legal fees. We estimate that the total expenses of this offering, including registration, filing and listing fees, printing fees and legal and accounting expenses, but excluding the underwriting discounts and commissions, will be approximately $              .

A prospectus in electronic format may be made available on the websites maintained by one or more underwriters, or selling group members, if any, participating in the offering. The underwriters may agree to allocate a number of shares to underwriters and selling group members for sale to their online brokerage account holders. Internet distributions will be allocated by the representatives to underwriters and selling group members that may make Internet distributions on the same basis as other allocations.

We have agreed, subject to specified exceptions, that we will not (i) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise dispose of, directly or indirectly, or file with the SEC a registration statement under the Securities Act relating to, any shares of our common stock or securities convertible into or exchangeable or exercisable for any shares of our common stock, or publicly disclose the intention to make any offer, sale, pledge, disposition or filing, or (ii) enter into any swap or other arrangement that transfers all or a portion of the economic consequences associated with the ownership of any shares of common stock or any such other securities (regardless of whether any of these transactions are to be settled by the delivery of shares of common stock or such other securities, in cash or otherwise), in each case without the prior written consent of J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC for a period of 90 days after the date of this prospectus.

Our directors and executive officers have entered into lock-up agreements with the underwriters prior to the commencement of this offering pursuant to which each of these persons or entities, with limited exceptions, for a period of 90 days after the date of this prospectus, may not, without the prior written consent of J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC, (i) offer, sell, assign, transfer, pledge, contract to sell, or otherwise dispose of, or publicly disclose the intention to make any offer, sale, pledge or disposition of, any shares of our common stock or securities convertible into or exercisable or exchangeable for our common stock (including, without limitation, shares of our common stock or any such securities which may be deemed to be beneficially owned by such officers and directors in accordance with the rules and regulations promulgated under the Exchange Act (such shares or securities, the "Beneficially Owned Shares")), (ii) enter into any swap, hedge or other agreement or arrangement that transfers in whole or in part, the economic risk of ownership of any Beneficially Owned Shares, our common stock or securities convertible into or exercisable or exchangeable for our common stock, or (iii) engage in any short selling of any Beneficially Owned Shares, our common stock or securities convertible into or exercisable or exchangeable for our common stock.

J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC may, in their sole discretion and at any time or from time to time before the termination of the 90 day restricted period, without public notice, release all or any portion of the securities subject to lock-up agreements. There are no existing agreements between the underwriters and us providing consent to the sale of shares prior to the expiration of the lock-up period. Sales of a substantial number of such shares upon expiration of the lock-up and market stand-off agreements, the perception that such sales may occur, or early release of these agreements, could cause our market price to fall or make it more difficult for you to sell your common stock at a time and price that you deem appropriate.

We have agreed to indemnify the several underwriters against certain liabilities, including liabilities under the Securities Act.

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In connection with this offering, the underwriters may engage in stabilizing transactions, which involves making bids for, purchasing and selling shares of common stock in the open market for the purpose of preventing or retarding a decline in the market price of the common stock while this offering is in progress. These stabilizing transactions may include making short sales of the common stock, which involves the sale by the underwriters of a greater number of shares of common stock than they are required to purchase in this offering, and purchasing shares of common stock on the open market to cover positions created by short sales. Short sales may be "covered" shorts, which are short positions in an amount not greater than the underwriters' option to purchase additional shares referred to above, or may be "naked" shorts, which are short positions in excess of that amount. The underwriters may close out any covered short position either by exercising their option to purchase additional shares, in whole or in part, or by purchasing shares in the open market. In making this determination, the underwriters will consider, among other things, the price of shares available for purchase in the open market compared to the price at which the underwriters may purchase shares through the option to purchase additional shares. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the common stock in the open market that could adversely affect investors who purchase in this offering. To the extent that the underwriters create a naked short position, they will purchase shares in the open market to cover the position.

The underwriters have advised us that, pursuant to Regulation M of the Securities Act, they may also engage in other activities that stabilize, maintain or otherwise affect the price of the common stock, including the imposition of penalty bids. This means that if the representatives of the underwriters purchase common stock in the open market in stabilizing transactions or to cover short sales, the representatives can require the underwriters that sold those shares as part of this offering to repay the underwriting discount received by them.

These activities may have the effect of raising or maintaining the market price of the common stock or preventing or retarding a decline in the market price of the common stock, and, as a result, the price of the common stock may be higher than the price that otherwise might exist in the open market. If the underwriters commence these activities, they may discontinue them at any time. The underwriters may carry out these transactions on NASDAQ, in the over-the-counter market or otherwise.

In addition, in connection with this offering certain of the underwriters (and selling group members) may engage in passive market making transactions in our common stock on NASDAQ prior to the pricing and completion of this offering. Passive market making consists of displaying bids on NASDAQ no higher than the bid prices of independent market makers and making purchases at prices no higher than these independent bids and effected in response to order flow. Net purchases by a passive market maker on each day are generally limited to a specified percentage of the passive market maker's average daily trading volume in the common stock during a specified period and must be discontinued when such limit is reached. Passive market making may cause the price of our common stock to be higher than the price that otherwise would exist in the open market in the absence of these transactions. If passive market making is commenced, it may be discontinued at any time.

Other than in the United States, no action has been taken by us or the underwriters that would permit a public offering of the securities offered by this prospectus in any jurisdiction where action for that purpose is required. The securities offered by this prospectus may not be offered or sold, directly or indirectly, nor may this prospectus or any other offering material or advertisements in connection with the offer and sale of any such securities be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus comes are advised to inform themselves about and to observe any restrictions

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relating to the offering and the distribution of this prospectus. This prospectus does not constitute an offer to sell or a solicitation of an offer to buy any securities offered by this prospectus in any jurisdiction in which such an offer or a solicitation is unlawful.

Canada

Shares of the common stock offered hereby may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of shares of the common stock offered hereby must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser's province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser's province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Dubai

This prospectus supplement relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority (the "DFSA"). This prospectus supplement is intended for distribution only to persons of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus supplement nor taken steps to verify the information set forth herein and has no responsibility for this prospectus supplement. The shares to which this prospectus supplement relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the shares offered should conduct their own due diligence on the shares. If you do not understand the contents of this prospectus supplement you should consult an authorized financial advisor.

European Economic Area

In relation to each Member State of the European Economic Area (the "EEA") which has implemented the Prospectus Directive (each, a "Relevant Member State"), an offer of our shares may not be made to the public in a Relevant Member State other than:

•

to any legal entity which is a qualified investor as defined in the Prospectus Directive;

•

to fewer than 150 natural or legal persons (other than qualified investors as defined in the Prospectus Directive), subject to obtaining the prior consent of the relevant dealer or dealers nominated by us for any such offer; or

•

in any other circumstances falling within Article 3(2) of the Prospectus Directive,

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provided that no such offer of our shares shall require us or any underwriter to publish a prospectus pursuant to Article 3 of the Prospectus Directive or supplement prospectus pursuant to Article 16 of the Prospectus Directive.

For the purposes of this description, the expression an "offer of our shares to the public" in relation to any of our shares in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and the shares to be offered so as to enable an investor to decide to purchase or subscribe for the shares, as the expression may be varied in that Relevant Member State by any measure implementing the Prospectus Directive in that member state, and the expression "Prospectus Directive" means European Union Directive 2003/71/EC (as amended by Directive 2010/73/EU and includes any relevant implementing measure in each Relevant Member State.

Neither this prospectus supplement nor the accompanying prospectus is a prospectus for the purposes of the Prospectus Directive. This prospectus supplement and the accompanying prospectus have been prepared on the basis that any offer of our shares in any Relevant Member State will be made pursuant to an exemption under the Prospectus Directive from the requirement to publish a prospectus for offers of shares. We have not authorized and do not authorize the making of any offer of securities through any financial intermediary on our behalf, other than offers made by the underwriters and their respective affiliates, with a view to the final placement of the securities as contemplated in this document. Accordingly, no purchaser of the shares, other than the underwriters, is authorized to make any further offer of shares on our behalf or on behalf of the underwriters.

Hong Kong

The shares may not be offered or sold by means of any document other than (i) in circumstances which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap.32, Laws of Hong Kong), or (ii) to "professional investors" within the meaning of the Securities and Futures Ordinance (Cap.571, Laws of Hong Kong) and any rules made thereunder, or (iii) in other circumstances which do not result in the document being a "prospectus" within the meaning of the Companies Ordinance (Cap.32, Laws of Hong Kong), and no advertisement, invitation or document relating to the shares may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to shares which are or are intended to be disposed of only to persons outside Hong Kong or only to "professional investors" within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

Japan

The securities have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (the Financial Instruments and Exchange Law) and each underwriter has agreed that it will not offer or sell any securities, directly or indirectly, in Japan or to, or for the benefit of, any resident of Japan (which term as used herein means any person resident in Japan, including any corporation or other entity organized under the laws of Japan), or to others for re-offering or resale, directly or indirectly, in Japan or to a resident of Japan, except pursuant to an exemption from the registration requirements of, and otherwise in compliance with, the Financial Instruments and Exchange Law and any other applicable laws, regulations and ministerial guidelines of Japan.

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Singapore

This prospectus has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the shares may not be circulated or distributed, nor may the shares be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the "SFA"), (ii) to a relevant person, or any person pursuant to Section 275(1A), and in accordance with the conditions, specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Where the shares are subscribed or purchased under Section 275 by a relevant person which is: (a) a corporation (which is not an accredited investor) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or (b) a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary is an accredited investor, shares, debentures and units of shares and debentures of that corporation or the beneficiaries' rights and interest in that trust shall not be transferable for 6 months after that corporation or that trust has acquired the shares under Section 275 except: (1) to an institutional investor under Section 274 of the SFA or to a relevant person, or any person pursuant to Section 275(1A), and in accordance with the conditions, specified in Section 275 of the SFA; (2) where no consideration is given for the transfer; or (3) by operation of law.

Switzerland

The shares may not be publicly offered in Switzerland and will not be listed on the SIX Swiss Exchange (the "SIX") or on any other stock exchange or regulated trading facility in Switzerland. This document has been prepared without regard to the disclosure standards for issuance prospectuses under art. 652a or art. 1156 of the Swiss Code of Obligations or the disclosure standards for listing prospectuses under art. 27 ff. of the SIX Listing Rules or the listing rules of any other stock exchange or regulated trading facility in Switzerland. Neither this document nor any other offering or marketing material relating to the shares or the offering may be publicly distributed or otherwise made publicly available in Switzerland.

Neither this prospectus supplement nor any other offering or marketing material relating to the offering, the issuer, the shares have been or will be filed with or approved by any Swiss regulatory authority. In particular, this prospectus supplement will not be filed with, and the offer of shares will not be supervised by, the Swiss Financial Market Supervisory Authority, and the offer of shares has not been and will not be authorized under the Swiss Federal Act on Collective Investment Schemes (the "CISA"). The investor protection afforded to acquirers of interests in collective investment schemes under the CISA does not extend to acquirers of shares.

United Kingdom

This document is only being distributed to and is only directed at (i) persons who are outside the United Kingdom or (ii) to investment professionals falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the "Order") or (iii) high net worth entities, and other persons to whom it may lawfully be communicated, falling with Article 49(2)(a) to (d) of the Order (all such persons together being referred to as "relevant persons"). The securities are only available to, and any invitation, offer or agreement to subscribe, purchase or otherwise acquire such securities will be engaged in only with, relevant persons. Any person who is not a relevant person should not act or rely on this document or any of its contents.

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Other relationships

The underwriters and their affiliates are full service financial institutions engaged in various activities, which may include sales and trading, commercial and investment banking, advisory, investment management, investment research, principal investment, hedging, market making, brokerage and other financial and nonfinancial activities and services. The underwriters and their affiliates may in the future provide, a variety of these services to the issuer and to persons and entities with relationships with the issuer, for which they received or will receive customary fees and expenses.

In the ordinary course of their various business activities, the underwriters and their affiliates, officers, directors and employees may purchase, sell or hold a broad array of investments and actively traded securities, derivatives, loans, commodities, currencies, credit default swaps and other financial instruments for their own account and for the accounts of their customers, and such investment and trading activities may involve or relate to assets, securities and/or instruments of the issuer (directly, as collateral securing other obligations or otherwise) and/or persons and entities with relationships with the issuer. The underwriters and their affiliates may also communicate independent investment recommendations, market color or trading ideas and/or publish or express independent research views in respect of such assets, securities or instruments and may at any time hold, or recommend to clients that they should acquire, long and/or short positions in such assets, securities and instruments.

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Validity of securities

The validity of the common stock being offered by this prospectus supplement will be passed upon for us by our counsel, Paul Hastings LLP, San Diego, California. Certain legal matters in connection with this offering will be passed upon for the underwriters by Simpson Thacher & Bartlett LLP, New York, New York.

Experts

The consolidated financial statements incorporated in this prospectus supplement by reference from the Company's Annual Report on Form 10-K for the fiscal year ended December 25, 2016, and the effectiveness of Kratos Defense & Security Solutions, Inc.'s internal control over financial reporting, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report, which is incorporated herein by reference. Such consolidated financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

Where you can find additional information

We file annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any document we file at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for more information about the operation of the public reference room. The SEC maintains an internet website that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC, including Kratos Defense & Security Solutions, Inc. The address of the SEC's website is www.sec.gov. You may also access our reports and proxy statements free of charge at our website, http://www.kratosdefense.com. The information contained in, or that can be accessed through, our website is not part of this prospectus supplement. The prospectus included in this filing is part of a registration statement filed by us with the SEC. The full registration statement can be obtained from the SEC, as indicated above, or from us.

Incorporation of certain documents by reference

The SEC allows us to incorporate by reference the information we file with it, which means that we can disclose important information to you by referring you to another document that we have filed separately with the SEC. The information incorporated by reference is considered to be a part of this prospectus supplement and the accompanying prospectus. We hereby incorporate by reference the following information or documents into this prospectus supplement:

•

our Annual Report on Form 10-K for the fiscal year ended December 25, 2016 filed with the SEC on February 27, 2017;

•

the portions of the Definitive Proxy Statement on Schedule 14A, filed with the SEC on April 14, 2017, that are incorporated by reference into Part III of our Annual Report on Form 10-K for the fiscal year ended December 25, 2016, filed with the SEC on February 27, 2017;

•

our Quarterly Reports on Form 10-Q for the quarterly periods ended March 26, 2017 and June 25, 2017, filed with the SEC on May 4, 2017 and July 27, 2017, respectively;

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our Current Reports on Form 8-K filed with the SEC on January 17, 2017, March 2, 2017, March 7, 2017 and June 6, 2017; and

•

the description of our common stock contained in our Registration Statement on Form 8-A (File No. 000-27231), filed under Section 12(g) of the Exchange Act on September 3, 1999, including any subsequent amendment or report filed for the purpose of amending such description.

Any information in any of the foregoing documents will automatically be deemed to be modified or superseded to the extent that information in this prospectus supplement or the accompanying prospectus or in a later filed document that is incorporated or deemed to be incorporated herein by reference modifies or replaces such information. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement.

We also incorporate by reference any future filings (other than information in current reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items) made with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, until we sell all of the securities offered by this prospectus supplement. Information in such future filings updates and supplements the information provided in this prospectus supplement. Any statements in any such future filings will automatically be deemed to modify and supersede any information in any document we previously filed with the SEC that is incorporated or deemed to be incorporated herein by reference to the extent that statements in the later filed document modify or replace such earlier statements.

Upon written or oral request, we will provide to you, without charge, a copy of any or all of the documents that are incorporated by reference into this prospectus supplement and the accompanying prospectus but not delivered with the prospectus, including exhibits which are specifically incorporated by reference into such documents. Requests should be directed to: Kratos Defense & Security Solutions, Inc., Attention: Investor Relations, 4820 Eastgate Mall, Suite 200, San Diego, California, 92121, telephone (858) 812-7300.

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PROSPECTUS

Kratos Defense & Security Solutions, Inc.

Common Stock
Preferred Stock
Debt Securities
Warrants
Rights
Units

        We may from time to time offer to sell any combination of the securities described in this prospectus, either individually or in units, in one or more offerings. In addition, certain selling security holders to be identified in supplements to this prospectus may offer and sell these securities from time to time.

        This prospectus provides a general description of the securities we may offer. Each time we sell securities, we will provide specific terms of the securities offered in a supplement to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. The prospectus supplement and any related free writing prospectus may also add, update or change information contained in this prospectus. You should carefully read this prospectus, the applicable prospectus supplement and any related free writing prospectus, as well as any documents incorporated by reference herein or therein before you invest in any securities. This prospectus may not be used to consummate a sale of securities unless accompanied by the applicable prospectus supplement.

        Our common stock is listed on The NASDAQ Global Select Market under the symbol "KTOS." The applicable prospectus supplement will contain information, where applicable, as to any other listing on The NASDAQ Global Select Market or any securities market or other exchange of the securities, if any, covered by the prospectus supplement.

        Investing in our securities involves risks. See "Risk Factors" beginning on page 4.

        The securities may be offered directly by us or by any selling security holder from time to time, through agents designated by us or to or through underwriters, brokers or dealers. We will provide specific information about any selling security holders in one or more supplements to this prospectus. For additional information on the methods of sale, you should refer to the section entitled "Plan of Distribution" in this prospectus. If any underwriters are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such underwriters and any applicable commissions or discounts will be set forth in a prospectus supplement or a related free writing prospectus. The price to the public of such securities and the net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement or a related free writing prospectus.

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        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

   

The date of this prospectus is September 5, 2017.

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ABOUT THIS PROSPECTUS

        This prospectus is a part of an automatic shelf registration statement that we filed with the Securities and Exchange Commission, or the SEC, as a "well-known seasoned issuer" as defined in Rule 405 under the Securities Act of 1933, as amended, or the Securities Act, utilizing a "shelf" registration process. Under this shelf registration process, we may sell any combination of the securities described in this prospectus in one or more offerings. In addition, selling security holders to be named in a prospectus supplement may sell certain of our securities from time to time. This prospectus provides you with a general description of the securities we may offer. Each time we or any selling security holder offers to sell securities under this shelf registration, we or the selling security holder will provide a prospectus supplement that will contain specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update or change information contained in this prospectus or in any documents that we have incorporated by reference into this prospectus. To the extent that any statement that we make in a prospectus supplement is inconsistent with statements made in this prospectus, the statement made in this prospectus will be deemed modified or superseded by those made in the prospectus supplement. You should read this prospectus, any applicable prospectus supplement and any related free writing prospectus, together with the information incorporated herein by reference as described under the heading "Where You Can Find Additional Information" and "Incorporation of Certain Information by Reference."

        You should rely only on the information that we have provided or incorporated by reference in this prospectus, any applicable prospectus supplement and any related free writing prospectus that we may authorize to be provided to you. We have not authorized any broker, dealer, salesperson or other person to give any information or to make any representation other than those contained or incorporated by reference in this prospectus, any applicable prospectus supplement or any related free writing prospectus that we may authorize to be provided to you. You must not rely upon any information or representation not contained or incorporated by reference in this prospectus, the accompanying prospectus supplement or related free writing prospectus. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you.

        This prospectus, the accompanying supplement to this prospectus and any related free writing prospectus, if any, do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the registered securities to which they relate, nor do this prospectus, the accompanying supplement to this prospectus or any related free writing prospectus, if any, constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction. You should not assume that the information contained in this prospectus, any applicable prospectus supplement or any related free writing prospectus is accurate on any date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference therein is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus, any applicable prospectus supplement or any related free writing prospectus is delivered or the applicable securities are sold on a later date.

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RISK FACTORS

        Investment in our securities involves risks. Prior to making a decision about investing in our securities, you should consider carefully all of the information included and incorporated by reference or deemed to be incorporated by reference in this prospectus or the applicable prospectus supplement, including the risk factors incorporated by reference herein from our Annual Report on Form 10-K for the year ended December 25, 2016, filed with the SEC on February 27, 2017, as updated by annual, quarterly and other reports and documents we file with the SEC after the date of this prospectus and that are incorporated by reference herein or in the applicable prospectus supplement or any free writing prospectus. Each of these risk factors could have a material adverse effect on our business, results of operations, financial position or cash flows, which may result in the loss of all or part of your investment. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently consider immaterial may also impair our business operations. If any of these risks actually occur, our business and financial results could be harmed. In that case, the trading price of our common stock or other securities could decline. To the extent a particular offering implicates additional known material risks, we will include a discussion of those risks in the applicable prospectus supplement.

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SPECIAL NOTE REGARDING FORWARD-LOOKING INFORMATION

        This prospectus and the documents incorporated herein by reference contain forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. These statements are based on our management's current beliefs, expectations and assumptions about future events, conditions and results and on information currently available to us. Discussions containing these forward-looking statements may be found, among other places, in the Sections entitled "Business," "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" incorporated by reference from our most recent Annual Report on Form 10-K and in our Quarterly Reports on Form 10-Q, as well as any amendments thereto, filed with the SEC.

        All statements, other than statements of historical fact, included or incorporated herein regarding our strategy, future operations, financial position, future revenues, projected costs, plans, prospects and objectives are forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as "may," "will," "should," "expect," "plan," "anticipate," "believe," "estimate," "predict," "potential," or "continue," the negative of such terms or other comparable terminology. Important risks and uncertainties that could cause our actual results or achievements to differ materially from the results or achievements reflected in our forward-looking statements include, but are not limited to: changes or cutbacks in spending or the appropriation of funding by the federal government, including the U.S. Department of Defense, which could cause delays, cancellations or reductions of key government contracts; bid protests; changes in the scope or timing of our projects; the timing, rescheduling or cancellation of significant customer contracts and agreements, or consolidation by or the loss of key customers; risks of adverse regulatory action or litigation; risks associated with debt leverage and the refinancing of outstanding debt; failure to successfully achieve our integration, cost reduction or divestiture strategies; risks related to security breaches, cybersecurity attacks or other significant disruptions of our information systems; and competition in the marketplace, which could reduce revenues and profit margins, as well as the additional risks and uncertainties included or incorporated herein.

        Such statements are based on currently available operating, financial and competitive information and are subject to various risks, uncertainties and assumptions that could cause actual results to differ materially from those anticipated or implied in our forward-looking statements due to a number of factors including, but not limited to, those set forth below under the section entitled "Risk Factors" in our most recent Annual Report on Form 10-K and in our Quarterly Reports on Form 10-Q, as well as any amendments thereto filed with the SEC. Given these risks, uncertainties and other factors, many of which are beyond our control, you should not place undue reliance on these forward-looking statements.

        Except as required by law, we assume no obligation to update these forward-looking statements publicly, or to revise any forward-looking statements to reflect events or developments occurring after the date of this prospectus, even if new information becomes available in the future.

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STATEMENT OF COMPUTATION OF RATIOS

        The following summary is qualified by the more detailed information appearing in the computation table found in Exhibit 12.1 to the registration statement of which this prospectus is a part and the historical financial statements, including the notes to those financial statements, incorporated by reference in this prospectus.

        The following table sets forth our ratio of earnings to fixed charges and the dollar amount of the coverage deficiency, if any, for the six month period ended June 25, 2017 and the five fiscal years in the period ended December 25, 2016. As of the date of this prospectus we have, and during all the periods presented we have had, no preferred stock outstanding; accordingly, we were not required to pay, and we have not declared or paid, any preferred stock dividends for the periods set forth below. Accordingly, our ratio of earnings to combined fixed charges and preferred stock dividends did not differ from the ratios presented below during any of these periods.

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USE OF PROCEEDS

        Except as described in any applicable prospectus supplement and in any free writing prospectuses in connection with a specific offering, we currently intend to use the net proceeds from the sale of the securities offered hereby for general corporate purposes, including, among other things, working capital requirements and potential repayment of indebtedness that may be outstanding at the time of any offering under this prospectus. We may also use a portion of the net proceeds to acquire or invest in businesses, services and technologies that are complementary to our own. Pending these uses, we intend to invest the net proceeds in investment-grade, interest-bearing securities. We will not receive any of the proceeds from sales of securities by selling security holders.

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DESCRIPTION OF CAPITAL STOCK

        The following description of our capital stock, together with any additional information we include in any applicable prospectus supplements or any free writing prospectuses that we may authorize to be delivered to you, summarizes the material terms and provisions of our capital stock that we may offer under this prospectus. While the terms we have summarized below will apply generally to any future capital stock that we may offer, we will describe the particular terms of any class or series of these securities in more detail in the applicable prospectus supplement or free writing prospectus. For the complete terms of our capital stock, please refer to our amended and restated certificate of incorporation, as amended, and our second amended and restated bylaws, as amended, that are incorporated by reference into the registration statement of which this prospectus is a part or may be incorporated by reference in this prospectus or any prospectus supplement. The terms of these securities may also be affected by the Delaware General Corporation Law, or the DGCL. The summary below and that contained in any prospectus supplement or free writing prospectus are qualified in their entirety by reference to our amended and restated certificate of incorporation, as amended, and our second amended and restated bylaws, as amended.

Common Stock

        We are authorized to issue 195,000,000 shares of common stock, of which 86,634,053 shares were issued and outstanding as of June 25, 2017. The holders of common stock possess exclusive voting rights in us, except to the extent our board of directors specifies voting power with respect to any other class of securities issued in the future. Each holder of our common stock is entitled to one vote for each share held of record on each matter submitted to a vote of stockholders, including the election of directors. Stockholders do not have any right to cumulate votes in the election of directors.

        Subject to preferences that may be granted to the holders of preferred stock, each holder of our common stock is entitled to share ratably in distributions to stockholders and to receive ratably such dividends as may be declared by our board of directors out of funds legally available therefor. In the event of our liquidation, dissolution or winding up, the holders of our common stock will be entitled to receive, after payment of all of our debts and liabilities and of all sums to which holders of any preferred stock may be entitled, the distribution of any of our remaining assets. Holders of our common stock have no conversion, exchange, sinking fund, redemption or appraisal rights (other than such as may be determined by our board of directors in its sole discretion) and have no preemptive rights to subscribe for any of our securities.

        All of the outstanding shares of our common stock are, and the shares of common stock issued upon the conversion of any securities convertible into our common stock will be, fully paid and non-assessable. The shares of common stock offered by this prospectus or upon the conversion of any preferred stock or debt securities or exercise of any warrants offered pursuant to this prospectus, when issued and paid for, will also be, fully paid and non-assessable.

        Our common stock is listed on The NASDAQ Global Select Market under the symbol "KTOS."

Preferred Stock

        We are authorized to issue 5,000,000 shares of preferred stock, none of which were issued and outstanding as of June 25, 2017. Our board is authorized to classify or reclassify any unissued portion of our authorized shares of preferred stock to provide for the issuance of shares of other classes or series, including preferred stock in one or more series. We may issue preferred stock from time to time in one or more classes or series, with the exact terms of each class or series established by our board. Without seeking stockholder approval, our board may issue preferred stock with voting and other rights that could adversely affect the voting power of the holders of our common stock. Additionally, the issuance of preferred stock may have the effect of decreasing the market price of the common stock.

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        The rights, preferences, privileges and restrictions of the preferred stock of each series will be fixed by the certificate of designation relating to each series. A prospectus supplement relating to each series will specify the terms of the preferred stock, including, but not limited to:

•

the distinctive designation and the maximum number of shares in the series;



•

the terms on which dividends, if any, will be paid;



•

the voting rights, if any, on the shares of the series;



•

the terms and conditions, if any, on which the shares of the series shall be convertible into, or exchangeable for, shares of any other class or classes of capital stock;



•

the terms on which the shares may be redeemed, if at all;



•

the liquidation preference, if any; and



•

any or all other preferences, rights, restrictions, including restrictions on transferability, and qualifications of shares of the series.

        The issuance of preferred stock may delay, deter or prevent a change in control.

        We will describe the specific terms of a particular series of preferred stock in the prospectus supplement relating to that series. The description of preferred stock above and the description of the terms of a particular series of preferred stock in the prospectus supplement are not complete. You should refer to the applicable certificate of designation for complete information. The prospectus supplement will contain a description of U.S. federal income tax consequences relating to the preferred stock.

Possible Anti-Takeover Effects of Delaware Law and our Charter Documents

        Provisions of the DGCL and our amended and restated certificate of incorporation, as amended, and our second amended and restated bylaws, as amended, could make it more difficult to acquire us by means of a tender offer, a proxy contest or otherwise, or to remove incumbent officers and directors. These provisions, summarized below, are expected to discourage certain types of coercive takeover practices and takeover bids that our board of directors may consider inadequate and to encourage persons seeking to acquire control of us to first negotiate with our board of directors. We believe that the benefits of increased protection of our ability to negotiate with the proponent of an unfriendly or unsolicited proposal to acquire or restructure us outweigh the disadvantages of discouraging takeover or acquisition proposals because, among other things, negotiation of these proposals could result in an improvement of their terms.

Delaware Anti-Takeover Statute

        We are subject to Section 203 of the DGCL, an anti-takeover statute. In general, Section 203 of the DGCL prohibits a publicly held Delaware corporation from engaging in a "business combination" with an "interested stockholder" for a period of three years following the time the person became an interested stockholder, unless the business combination or the acquisition of shares that resulted in a stockholder becoming an interested stockholder is approved in a prescribed manner. Generally, a "business combination" includes a merger, asset or stock sale, or other transaction resulting in a financial benefit to the interested stockholder. Generally, an "interested stockholder" is a person who, together with affiliates and associates, owns (or within three years prior to the determination of interested stockholder status did own) 15% or more of a corporation's voting stock. The existence of this provision would be expected to have an anti-takeover effect with respect to transactions not approved in advance by our board of directors, including discouraging attempts that might result in a premium over the market price for the shares of common stock held by our stockholders.

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Election and Removal of Directors

        Our board of directors is elected annually by all holders of our capital stock. To be eligible for election or appointment to the board of directors, an individual must meet certain director qualification requirements set forth in our second amended and restated bylaws, as amended. At a special meeting of stockholders, directors may be removed without cause by the affirmative vote of the holders of at least a majority of the outstanding shares entitled to vote on such removal.

Amendment

        The affirmative vote of the holders of at least 66 ²/3% of the voting power of all of the then-outstanding shares of our voting stock, voting together as a single class, is required to, among other things, alter, amend or repeal certain provisions of our amended and restated certificate of incorporation, as amended, including those related to the election and removal of the board of directors, amendment of our second amended and restated bylaws, as amended, and amended and restated certificate of incorporation, as amended, restrictions against stockholder actions by written consent and the indemnification of officers and directors.

        Our second amended and restated bylaws, as amended, may only be amended (or new bylaws adopted) by the board of directors or the affirmative vote of the holders of at least 66 ²/3% of the voting power of all of the then-outstanding shares of our voting stock.

Size of Board and Vacancies

        Pursuant to our amended and restated certificate of incorporation, as amended, and our second amended and restated bylaws, as amended, our board of directors has the exclusive right to fix the size of the board and to fill any vacancies resulting from death, resignation, disqualification or removal as well as any newly created directorships arising from an increase in the size of the board.

Special Stockholder Meetings

        Our second amended and restated bylaws, as amended, provide that only a majority of the total number of directors then in office may call a special meeting of the stockholders, and any business conducted at any special meeting must have been properly brought before the meeting. To be properly brought before a meeting, business must be specified in the notice of meeting (or any supplement thereto) given by or at the direction of our board of directors, otherwise properly brought before the meeting by or at the direction of our board of directors, or otherwise properly brought before the meeting by a stockholder, but, in the case of a special meeting, if and only if the notice of the meeting provides for business to be brought before the meeting by a stockholder.

Stockholder Action by Unanimous Written Consent

        Our amended and restated certificate of incorporation, as amended, expressly eliminates the right of our stockholders to act by written consent. Stockholder action must take place at the annual or a special meeting of our stockholders.

Requirements for Advance Notification of Stockholder Nominations and Proposals

        Our second amended and restated bylaws, as amended, establish advance notice procedures with respect to stockholder proposals and nomination of candidates for election as directors other than nominations made by or at the direction of our board of directors or a committee of our board of directors.

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No Cumulative Voting

        The DGCL provides that stockholders are denied the right to cumulate votes in the election of directors unless our certificate of incorporation provides otherwise. Our amended and restated certificate of incorporation, as amended, does not provide for cumulative voting.

Undesignated Preferred Stock

        The authority that will be possessed by our board of directors to issue preferred stock could potentially be used to discourage attempts by third parties to obtain control of our company through a merger, tender offer, proxy contest or otherwise by making such attempts more difficult or more costly. Our board of directors may issue preferred stock with voting rights or conversion rights that, if exercised, could adversely affect the voting power of the holders of our common stock.

Authorized but Unissued Shares

        Our authorized but unissued shares of common stock and preferred stock will be available for future issuance without stockholder approval. We may use additional shares for a variety of purposes, including future public offerings to raise additional capital, to fund acquisitions and as employee compensation. The existence of authorized but unissued shares of common stock and preferred stock could render more difficult or discourage an attempt to obtain control of us by means of a proxy contest, tender offer, merger or otherwise.

Transfer Agent and Registrar

        The transfer agent and registrar for our common stock is Wells Fargo Bank, N.A., Shareowner Services. Its address is 161 North Concord Exchange Street, South Saint Paul, MN, 55075 and its telephone number is (800) 468-9716. The transfer agent for any series of preferred stock that we may offer under this prospectus will be named and described in the prospectus supplement for that series.

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DESCRIPTION OF DEBT SECURITIES

        The following description, together with the additional information we include in any applicable prospectus supplements or free writing prospectuses, summarizes the material terms and provisions of the debt securities that we may offer under this prospectus. We may issue debt securities, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. While the terms we have summarized below will apply generally to any future debt securities we may offer under this prospectus, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement or free writing prospectus. The terms of any debt securities we offer under a prospectus supplement may differ from the terms we describe below. Unless the context requires otherwise, whenever we refer to the "indentures," we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

        We will issue any senior debt securities under the senior indenture that we will enter into with the trustee named in the senior indenture. We will issue any subordinated debt securities under the subordinated indenture and any supplemental indentures that we will enter into with the trustee named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement, of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

        The indentures will be qualified under the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act. We use the term "trustee" to refer to either the trustee under the senior indenture or the trustee under the subordinated indenture, as applicable.

        The following summaries of material provisions of the senior debt securities, the subordinated debt securities and the indentures are subject to, and qualified in their entirety by reference to, all of the provisions of the indenture and any supplemental indentures applicable to a particular series of debt securities. We urge you to read the applicable prospectus supplements and any related free writing prospectuses related to the debt securities that we may offer under this prospectus, as well as the complete indentures that contains the terms of the debt securities. Except as we may otherwise indicate, the terms of the senior indenture and the subordinated indenture are identical.

General

        The terms of each series of debt securities will be established by or pursuant to a resolution of our board of directors and set forth or determined in the manner provided in an officers' certificate or by a supplemental indenture. Debt securities may be issued in separate series without limitation as to aggregate principal amount. We may specify a maximum aggregate principal amount for the debt securities of any series. We will describe in the applicable prospectus supplement the terms of the series of debt securities being offered, including:

•

the title;



•

the principal amount being offered, and if a series, the total amount authorized and the total amount outstanding;



•

any limit on the amount that may be issued;



•

whether or not we will issue the series of debt securities in global form, and, if so, the terms and who the depositary will be;



•

the maturity date;

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•

whether and under what circumstances, if any, we will pay additional amounts on any debt securities held by a person who is not a U.S. person for tax purposes, and whether we can redeem the debt securities if we have to pay such additional amounts;



•

the annual interest rate, which may be fixed or variable, or the method for determining the rate and the date interest will begin to accrue, the dates interest will be payable and the regular record dates for interest payment dates or the method for determining such dates;



•

whether or not the debt securities will be secured or unsecured, and the terms of any secured debt;



•

the terms of the subordination of any series of subordinated debt;



•

the place where payments will be payable;



•

restrictions on transfer, sale or other assignment, if any;



•

our right, if any, to defer payment of interest and the maximum length of any such deferral period;



•

the date, if any, after which, and the price at which, we may, at our option, redeem the series of debt securities pursuant to any optional or provisional redemption provisions and the terms of those redemption provisions;



•

provisions for a sinking fund purchase or other analogous fund, if any, including the date, if any, on which, and the price at which we are obligated, pursuant thereto or otherwise, to redeem, or at the holder's option, to purchase, the series of debt securities and the currency or currency unit in which the debt securities are payable;



•

whether the indenture will restrict our ability or the ability of our subsidiaries to:



•

incur additional indebtedness;



•

issue additional securities;



•

create liens;



•

pay dividends or make distributions in respect of our capital stock or the capital stock of our subsidiaries;



•

redeem capital stock;



•

place restrictions on our subsidiaries' ability to pay dividends, make distributions or transfer assets;



•

make investments or other restricted payments;



•

sell, transfer or otherwise dispose of assets;



•

enter into sale-leaseback transactions;



•

engage in transactions with stockholders or affiliates;



•

issue or sell stock of our subsidiaries; or



•

effect a consolidation or merger;



•

whether the indenture will require us to maintain any interest coverage, fixed charge, cash flow-based, asset-based or other financial ratios;



•

information describing any book-entry features;



•

the applicability of the provisions in the indenture on discharge;

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•

whether the debt securities are to be offered at a price such that they will be deemed to be offered at an "original issue discount" as defined in paragraph (a) of Section 1273 of the Internal Revenue Code of 1986, as amended;



•

the denominations in which we will issue the series of debt securities, if other than denominations of $1,000 and any integral multiple thereof;



•

the currency of payment of debt securities if other than U.S. dollars and the manner of determining the equivalent amount in U.S. dollars; and



•

any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities, including any additional events of default or covenants provided with respect to the debt securities, and any terms that may be required by us or advisable under applicable laws or regulations.

        U.S. federal income tax consequences applicable to debt securities sold at an original issue discount will be described in the applicable prospectus supplement. In addition, U.S. federal income tax or other consequences applicable to any debt securities which are denominated in a currency or currency unit other than U.S. dollars may be described in the applicable prospectus supplement.

Conversion or Exchange Rights

        We will set forth in the applicable prospectus supplement the terms under which a series of debt securities may be convertible into or exchangeable for our common stock, our preferred stock or other securities (including securities of a third party). We will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of our common stock, our preferred stock or other securities (including securities of a third party) that the holders of the series of debt securities receive would be subject to adjustment.

Consolidation, Merger or Sale

        Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the indentures will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquiror of such assets must assume all of our obligations under the indentures or the debt securities, as appropriate. If the debt securities are convertible into or exchangeable for our other securities or securities of other entities, the person with whom we consolidate or merge or to whom we sell all of our property must make provisions for the conversion of the debt securities into securities that the holders of the debt securities would have received if they had converted the debt securities before the consolidation, merger or sale.

Events of Default under the Indenture

        Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the following are events of default under the indentures with respect to any series of debt securities that we may issue:

•

if we fail to pay interest when due and payable and our failure continues for 90 days and the time for payment has not been extended;



•

if we fail to pay the principal, premium or sinking fund payment, if any, when due and payable and the time for payment has not been extended;



•

if we fail to observe or perform any other covenant contained in the debt securities or the indentures, other than a covenant specifically relating to another series of debt securities, and

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our failure continues for 90 days after we receive notice from the trustee or we and the trustee receive notice from the holders of at least 25% in aggregate principal amount of the outstanding debt securities of the applicable series; and

•

if specified events of bankruptcy, insolvency or reorganization occur.

        We will describe in each applicable prospectus supplement any additional events of default relating to the relevant series of debt securities. If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may declare the unpaid principal, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default arises due to the occurrence of certain specified bankruptcy, insolvency or reorganization events, the unpaid principal, premium, if any, and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the trustee or any holder.

        The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any such waiver shall cure the default or event of default.

        Subject to the terms of the applicable indenture, if an event of default under an indenture shall occur and be continuing, the trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such holders have offered the trustee reasonable indemnity or security satisfactory to it against any loss, liability or expense. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or power conferred on the trustee, with respect to the debt securities of that series, provided that:

•

the direction so given by the holder is not in conflict with any law or the applicable indenture; and



•

subject to its duties under the Trust Indenture Act, the trustee need not take any action that might involve it in personal liability or might be unduly prejudicial to the holders not involved in the proceeding.

        The indentures provide that if an event of default has occurred and is continuing, the trustee will be required in the exercise of its powers to use the degree of care that a prudent person would use in the conduct of its own affairs. The trustee, however, may refuse to follow any direction that conflicts with law or the indenture, or that the trustee determines is unduly prejudicial to the rights of any other holder of the relevant series of debt securities, or that would involve the trustee in personal liability. Prior to taking any action under the indentures, the trustee will be entitled to indemnification against all costs, expenses and liabilities that would be incurred by taking or not taking such action.

        A holder of the debt securities of any series will have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies only if:

•

the holder has given written notice to the trustee of a continuing event of default with respect to that series;



•

the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series have made a written request and such holders have offered reasonable indemnity to

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the trustee or security satisfactory to it against any loss, liability or expense to be incurred in compliance with instituting the proceeding as trustee; and

•

the trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series other conflicting directions within 60 days after the notice, request and offer.

        These limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment of the principal, premium, if any, or interest on, the debt securities.

        We will periodically file statements with the trustee regarding our compliance with specified covenants in the indentures.

        The indentures provide that if a default occurs and is continuing and is actually known to a responsible officer of the trustee, the trustee must mail to each holder notice of the default within 45 days after it occurs, unless such default has been cured. Except in the case of a default in the payment of principal or premium of, or interest on, any debt security or certain other defaults specified in an indenture, the trustee shall be protected in withholding such notice if and so long as the board of directors, the executive committee or a trust committee of directors, or responsible officers of the trustee, in good faith determine that withholding notice is in the best interests of holders of the relevant series of debt securities.

Modification of Indenture; Waiver

        Subject to the terms of the indenture for any series of debt securities that we may issue, we and the trustee may change an indenture without the consent of any holders with respect to the following specific matters:

•

to fix any ambiguity, defect or inconsistency in the indenture;



•

to comply with the provisions described above under "—Consolidation, Merger or Sale";



•

to comply with any requirements of the SEC in connection with the qualification of any indenture under the Trust Indenture Act;



•

to add to, delete from or revise the conditions, limitations and restrictions on the authorized amount, terms or purposes of issue, authentication and delivery of debt securities, as set forth in such indenture;



•

to provide for the issuance of, and establish the form and terms and conditions of, the debt securities of any series as provided under "—General," to establish the form of any certifications required to be furnished pursuant to the terms of the indenture or any series of debt securities, or to add to the rights of the holders of any series of debt securities;



•

to evidence and provide for the acceptance of appointment hereunder by a successor trustee;



•

to provide for uncertificated debt securities in addition to or in place of certificated debt securities and to make all appropriate changes for such purpose;



•

to add such new covenants, restrictions, conditions or provisions for the protection of the holders, and to make the occurrence, or the occurrence and the continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default or to surrender any right or power conferred to us in the indenture; or



•

to change anything that does not materially adversely affect the interests of any holder of debt securities of any series in any material respect; provided that any amendment made solely to conform the provisions of the indenture to the corresponding description of the debt securities contained in the applicable prospectus or prospectus supplement shall be deemed not to

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adversely affect the interests of the holders of such debt securities; provided further, that in connection with any such amendment we will provide the trustee with an officers' certificate certifying that such amendment will not adversely affect the rights or interests of the holders of such debt securities.

        In addition, under the indentures, the rights of holders of a series of debt securities may be changed by us and the trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series that is affected. However, unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, we and the trustee may only make the following changes with the consent of each holder of any outstanding debt securities affected:

•

extending the fixed maturity of the series of debt securities;



•

reducing the principal amount, reducing the rate of or extending the time of payment of interest, or reducing any premium payable upon the redemption of any debt securities;



•

reducing the percentage of debt securities, the holders of which are required to consent to any amendment, supplement, modification or waiver;



•

changing any of our obligations to pay additional amounts;



•

reducing the amount of principal of an original issue discount security or any other note payable upon acceleration of the maturity thereof;



•

changing the currency in which any note or any premium or interest is payable;



•

impairing the right to enforce any payment on or with respect to any note;



•

adversely changing the right to convert or exchange, including decreasing the conversion rate or increasing the conversion price of, such note, if applicable;



•

in the case of the subordinated indenture, modifying the subordination provisions in a manner adverse to the holders of the subordinated debt securities;



•

if the debt securities are secured, changing the terms and conditions pursuant to which the debt securities are secured in a manner adverse to the holders of the secured debt securities;



•

reducing the requirements contained in the applicable indenture for quorum or voting;



•

changing any of our obligations to maintain an office or agency in the places and for the purposes required by the indentures; or



•

modifying any of the above provisions set forth in this paragraph.

Discharge

        Each indenture provides that, subject to the terms of the indenture and any limitation otherwise provided in the prospectus supplement applicable to a particular series of debt securities, we may elect to be discharged from our obligations with respect to one or more series of debt securities, except for specified obligations, including obligations to:

•

register the transfer or exchange of debt securities of the series;



•

replace stolen, lost or mutilated debt securities of the series;



•

maintain paying agencies;



•

hold monies for payment in trust;



•

recover excess money held by the trustee;

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•

compensate and indemnify the trustee; and



•

appoint any successor trustee.

        In order to exercise our rights to be discharged, we must deposit with the trustee money or government obligations sufficient to pay all the principal of, and any premium and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

        We will issue the debt securities of each series only in fully registered form without coupons and, unless we otherwise specify in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indentures provide that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company or another depositary named by us and identified in a prospectus supplement with respect to that series. See "Legal Ownership of Securities" below for a further description of the terms relating to any book-entry securities.

        At the option of the holder, subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the debt securities of any series can exchange the debt securities for other debt securities of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

        Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, we will impose no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

        We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.

        If we elect to redeem the debt securities of any series, we will not be required to:

•

issue, register the transfer of, or exchange any debt securities of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities that may be selected for redemption and ending at the close of business on the day of the mailing; or



•

register the transfer of or exchange any debt securities so selected for redemption, in whole or in part, except the unredeemed portion of any debt securities we are redeeming in part.

Information Concerning the Trustee

        The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture and is under no obligation to exercise any of the powers given it by the indentures at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur. However, upon an event of default under an

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indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs.

Payment and Paying Agents

        Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest payment.

        We will pay principal of and any premium and interest on the debt securities of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, we will make interest payments by check that we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in the applicable prospectus supplement, we will designate the corporate trust office of the trustee in the City of New York as our sole paying agent for payments with respect to debt securities of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the debt securities of a particular series. We will maintain a paying agent in each place of payment for the debt securities of a particular series.

        All money we pay to a paying agent or the trustee for the payment of the principal of or any premium or interest on any debt securities that remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the debt security thereafter may look only to us for payment thereof.

Governing Law

        The indentures and the debt securities will be governed by and construed in accordance with the laws of the State of New York, except to the extent that the Trust Indenture Act is applicable.

Ranking Debt Securities

        The subordinated debt securities will be unsecured and will be subordinate and junior in priority of payment to certain of our other indebtedness to the extent described in a prospectus supplement. The subordinated indenture does not limit the amount of subordinated debt securities that we may issue. It also does not limit us from issuing any other secured or unsecured debt.

        The senior debt securities will be unsecured and will rank equally in right of payment to all our other senior unsecured debt. The senior indenture does not limit the amount of senior debt securities that we may issue. It also does not limit us from issuing any other secured or unsecured debt.

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DESCRIPTION OF WARRANTS

        The following description, together with the additional information we may include in any applicable prospectus supplements and free writing prospectuses, summarizes the material terms and provisions of the warrants that we may offer under this prospectus, which may consist of warrants to purchase common stock, preferred stock or debt securities and may be issued in one or more series. Warrants may be offered independently or together with common stock, preferred stock or debt securities offered by any prospectus supplement, and may be attached to or separate from those securities. While the terms we have summarized below will apply generally to any warrants that we may offer under this prospectus, we will describe the particular terms of any series of warrants that we may offer in more detail in the applicable prospectus supplement and any applicable free writing prospectus. The terms of any warrants offered under a prospectus supplement may differ from the terms described below. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness.

        We will issue the warrants under a warrant agreement that we will enter into with a warrant agent to be selected by us. The warrant agent will act solely as an agent of ours in connection with the warrants and will not act as an agent for the holders or beneficial owners of the warrants. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from a current report on Form 8-K that we file with the SEC, the form of warrant agreement, including a form of warrant certificate, that describes the terms of the particular series of warrants we are offering before the issuance of the related series of warrants. The following summaries of material provisions of the warrants and the warrant agreements are subject to, and qualified in their entirety by reference to, all the provisions of the warrant agreement and warrant certificate applicable to a particular series of warrants. We urge you to read the applicable prospectus supplement and any applicable free writing prospectus related to the particular series of warrants that we sell under this prospectus, as well as the complete warrant agreements and warrant certificates that contain the terms of the warrants.

General

        We will describe in the applicable prospectus supplement the terms relating to a series of warrants, including:

•

the offering price and aggregate number of warrants offered;



•

the currency for which the warrants may be purchased;



•

if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;



•

if applicable, the date on and after which the warrants and the related securities will be separately transferable;



•

in the case of warrants to purchase debt securities, the principal amount of debt securities purchasable upon exercise of one warrant and the price at, and currency in which, this principal amount of debt securities may be purchased upon such exercise;



•

in the case of warrants to purchase common stock or preferred stock, the number of shares of common stock or preferred stock, as the case may be, purchasable upon the exercise of one warrant and the price at which these shares may be purchased upon such exercise;



•

the effect of any merger, consolidation, sale or other disposition of our business on the warrant agreements and the warrants;

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•

the terms of any rights to redeem or call the warrants;



•

any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;



•

the dates on which the right to exercise the warrants will commence and expire;



•

the manner in which the warrant agreements and warrants may be modified;



•

United States federal income tax consequences of holding or exercising the warrants;



•

the terms of the securities issuable upon exercise of the warrants; and



•

any other specific terms, preferences, rights or limitations of or restrictions on the warrants.

        Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including:

•

in the case of warrants to purchase debt securities, the right to receive payments of principal of, or premium, if any, or interest on, the debt securities purchasable upon exercise or to enforce covenants in the applicable indenture; or



•

in the case of warrants to purchase common stock or preferred stock, the right to receive dividends, if any, or, payments upon our liquidation, dissolution or winding up or to exercise voting rights, if any.

Exercise of Warrants

        Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

        Holders of the warrants may exercise the warrants by delivering the warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent in immediately available funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of the warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to the warrant agent.

        Upon receipt of the required payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the securities purchasable upon such exercise. If fewer than all of the warrants represented by the warrant certificate are exercised, then we will issue a new warrant certificate for the remaining amount of warrants. If we so indicate in the applicable prospectus supplement, holders of the warrants may surrender securities as all or part of the exercise price for warrants.

Enforceability of Rights by Holders of Warrants

        Each warrant agent will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

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DESCRIPTION OF RIGHTS

General

        We may issue rights to purchase common stock or preferred stock. This prospectus and any accompanying prospectus supplement will contain the material terms and conditions for each right. The accompanying prospectus supplement may add, update or change the terms and conditions of the rights as described in this prospectus.

        We will describe in the applicable prospectus supplement the terms and conditions of the issue of rights being offered, the rights agreement relating to the rights and the rights certificates representing the rights, including, as applicable:

•

the title of the rights;



•

the date of determining the stockholders entitled to the rights distribution;



•

the title, aggregate number of shares of common stock or preferred stock purchasable upon exercise of the rights;



•

the exercise price;



•

the currencies in which the rights are being offered;



•

the aggregate number of rights issued;



•

the date, if any, on and after which the rights will be separately transferable;



•

the date on which the right to exercise the rights will commence and the date on which the right will expire; and



•

any other terms of the rights, including terms, procedures and limitations relating to the distribution, exchange and exercise of the rights.

Exercise of Rights

        Each right will entitle the holder of rights to purchase for cash the principal amount of shares of common stock or preferred stock at the exercise price provided in the applicable prospectus supplement. Rights may be exercised at any time up to the close of business on the expiration date for the rights provided in the applicable prospectus supplement. After the close of business on the expiration date, all unexercised rights will be void.

        Holders may exercise rights as described in the applicable prospectus supplement. Upon receipt of payment and the rights certificate properly completed and duly executed at the corporate trust office of the rights agent or any other office indicated in the prospectus supplement, we will, as soon as practicable, forward the shares of common stock or preferred stock purchasable upon exercise of the rights. If less than all of the rights issued in any rights offering are exercised, we may offer any unsubscribed securities directly to persons other than stockholders, to or through agents, underwriters, brokers or dealers or through a combination of such methods, including pursuant to standby underwriting arrangements, as described in the applicable prospectus supplement.

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DESCRIPTION OF UNITS

        The following description, together with the additional information we may include in any applicable prospectus supplements and free writing prospectuses, summarizes the material terms and provisions of the units that we may offer under this prospectus. While the terms we have summarized below will apply generally to any units that we may offer under this prospectus, we will describe the particular terms of any series of units in more detail in the applicable prospectus supplement. The terms of any units offered under a prospectus supplement may differ from the terms described below. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness.

        We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from a current report on Form 8-K that we file with the SEC, the form of unit agreement that describes the terms of the series of units we are offering, and any supplemental agreements, before the issuance of the related series of units. The following summaries of material terms and provisions of the units are subject to, and qualified in their entirety by reference to, all the provisions of the unit agreement and any supplemental agreements applicable to a particular series of units. We urge you to read the applicable prospectus supplements related to the particular series of units that we sell under this prospectus, as well as the complete unit agreement and any supplemental agreements that contain the terms of the units.

General

        We may issue units comprised of one or more debt securities, shares of common stock, shares of preferred stock and warrants in any combination. Each unit will be issued so that the holder of the unit is also the holder of each security included in the unit. Thus, the holder of a unit will have the rights and obligations of a holder of each included security. The unit agreement under which a unit is issued may provide that the securities included in the unit may not be held or transferred separately, at any time or at any time before a specified date.

        We will describe in the applicable prospectus supplement the terms of the series of units, including:

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the designation and terms of the units and of the securities comprising the units, including whether and under what circumstances those securities may be held or transferred separately;



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any provisions of the governing unit agreement that differ from those described below; and



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any provisions for the issuance, payment, settlement, transfer or exchange of the units or of the securities comprising the units.

        The provisions described in this section, as well as those described under "Description of Capital Stock," "Description of Debt Securities" and "Description of Warrants" will apply to each unit and to any common stock, preferred stock, debt security or warrant included in each unit, respectively.

Issuance in Series

        We may issue units in such amounts and in numerous distinct series as we determine.

Enforceability of Rights by Holders of Units

        Each unit agent will act solely as our agent under the applicable unit agreement and will not assume any obligation or relationship of agency or trust with any holder of any unit. A single bank or trust company may act as unit agent for more than one series of units. A unit agent will have no duty or responsibility in case of any default by us under the applicable unit agreement or unit, including any

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duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a unit may, without the consent of the related unit agent or the holder of any other unit, enforce by appropriate legal action its rights as holder under any security included in the unit.

        We, the unit agents and any of their agents may treat the registered holder of any unit certificate as an absolute owner of the units evidenced by that certificate for any purpose and as the person entitled to exercise the rights attaching to the units so requested, despite any notice to the contrary. See "Legal Ownership of Securities."

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LEGAL OWNERSHIP OF SECURITIES

        We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee, depositary, warrant agent or other agent maintain for this purpose as the "holders" of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as "indirect holders" of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

        We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary's book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

        Only the person in whose name a security is registered is recognized as the holder of that security. Global securities will be registered in the name of the depositary. Consequently, for global securities, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

        As a result, investors in a global security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary's book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not legal holders, of the securities.

Street Name Holders

        We may terminate a global security or issue securities that are not issued in global form. In these cases, investors may choose to hold their securities in their own names or in "street name." Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

        For securities held in street name, we or any applicable trustee or depositary will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we or any such trustee or depositary will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not legal holders, of those securities.

Legal Holders

        Our obligations, as well as the obligations of any applicable trustee, agent or third party employed by us or a trustee or any agents, run only to the legal holders of the securities. We do not have

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obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

        For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with its participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, to relieve us of the consequences of a default or of our obligation to comply with a particular provision of an indenture, or for other purposes. In such an event, we would seek approval only from the legal holders, and not the indirect holders, of the securities. Whether and how the legal holders contact the indirect holders is up to the legal holders.

        When we refer to "you" in this prospectus, we mean those who invest in the securities being offered by this prospectus, whether they are the holders or only indirect holders of those securities. When we refer to "your securities" in this prospectus, we mean the securities in which you will hold a direct or indirect interest.

Special Considerations for Indirect Holders

        If you hold securities through a bank, broker or other financial institution, either in book-entry form because the securities are represented by one or more global securities or in street name, you should check with your own institution to find out:

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how it handles securities payments and notices;



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whether it imposes fees or charges;



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how it would handle a request for the holders' consent, if ever required;



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whether and how you can instruct it to send you securities registered in your own name so you can be a legal holder, if that is permitted in the future;



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how it would exercise rights under the securities if there were a default or other event triggering the need for holders to act to protect their interests; and



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if the securities are in book-entry form, how the depositary's rules and procedures will affect these matters.

Global Securities

        A global security is a security that represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

        Each security issued in book-entry form will be represented by a global security that we issue to, deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, The Depository Trust Company, New York, New York, known as DTC, will be the depositary for all securities issued in book-entry form.

        A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under "—Special Situations When A Global Security Will Be Terminated." As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and legal holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by

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means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a legal holder of the security, but only an indirect holder of a beneficial interest in the global security.

        If the prospectus supplement for a particular security indicates that the security will be issued as a global security, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations For Global Securities

        As an indirect holder, an investor's rights relating to a global security will be governed by the account rules of the investor's financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

        If securities are issued only as global securities, an investor should be aware of the following:

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an investor cannot cause the securities to be registered in his or her name, and cannot obtain non-global certificates for his or her interest in the securities, except in the special situations we describe below;



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an investor will be an indirect holder and must look to his or her own bank or broker for payments on the securities and protection of his or her legal rights relating to the securities, as we describe above;



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an investor may not be able to sell interests in the securities to some insurance companies and to other institutions that are required by law to own their securities in non-book-entry form;



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an investor may not be able to pledge his or her interest in the global security in circumstances where certificates representing the securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;



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the depositary's policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to an investor's interest in the global security. We and any applicable trustee have no responsibility for any aspect of the depositary's actions or for its records of ownership interests in the global security. We and the trustee also do not supervise the depositary in any way;



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the depositary may, and we understand that DTC will, require that those who purchase and sell interests in the global security within its book-entry system use immediately available funds, and your broker or bank may require you to do so as well; and



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financial institutions that participate in the depositary's book-entry system, and through which an investor holds its interest in the global security, may also have their own policies affecting payments, notices and other matters relating to the securities. There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When A Global Security Will Be Terminated

        In a few special situations described below, a global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult

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their own banks or brokers to find out how to have their interests in securities transferred to their own names, so that they will be direct holders. We have described the rights of holders and street name investors above.

        A global security will terminate when the following special situations occur:

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if the depositary notifies us that it is unwilling, unable or no longer qualified to continue as depositary for that global security and we do not appoint another institution to act as depositary within 90 days;



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if we notify any applicable trustee that we wish to terminate that global security; or



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if an event of default has occurred with regard to securities represented by that global security and has not been cured or waived.

        The applicable prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the prospectus supplement. If a global security is terminated, only the depositary, and not we, the trustee, the agent or other third party, as applicable, is responsible for deciding the names of the institutions in whose names the securities represented by the global security will be registered and, therefore, who will be the holders of those securities.

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SELLING SECURITY HOLDERS

        If the registration statement of which this prospectus forms a part is used by selling security holders for the resale of any securities registered thereunder pursuant to a registration rights agreement to be entered into by us with such selling security holders or otherwise, information about such selling security holders, their beneficial ownership of our securities and their relationship with us will be set forth in a prospectus supplement, any free writing prospectus or in filings we make with the SEC under the Exchange Act that are incorporated by reference into the registration statement.

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PLAN OF DISTRIBUTION

        We, or the applicable selling security holders, may sell the securities being offered hereby in one or more of the following ways from time to time:

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through agents to the public or to investors;



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to underwriters, brokers or dealers for resale to the public or to investors;



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in "at the market offerings" within the meaning of Rule 415(a)(4) under the Securities Act, to or through a market maker or into an existing trading market, on an exchange or otherwise;



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directly to investors;



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through a combination of any of these methods of sale; or



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through any other methods described in a prospectus supplement.

        We will set forth in a prospectus supplement the terms of that particular offering of securities, including:

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the name or names of any agents or underwriters, brokers or dealers and the amount of shares underwritten or purchased by each of them;



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the purchase price of the securities being offered and the proceeds we will receive from the sale;



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any over-allotment options under which underwriters may purchase additional securities from us;



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any agency fees or underwriting discounts and other items constituting agents' or underwriters' compensation;



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any initial public offering price;



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any discounts or concessions allowed or reallowed or paid to brokers or dealers; and



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any securities exchanges or markets on which such securities may be listed.

        We may designate agents who agree to use their reasonable efforts to solicit purchases of our securities for the period of their appointment or to sell our securities on a continuing basis.

        If we use underwriters for a sale of securities, the underwriters will acquire the securities for their own account. The underwriters may resell the securities in one or more transactions, including negotiated transactions, at a fixed public offering price, at varying prices determined at the time of sale, at prices related to prevailing market prices or at negotiated prices. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. The underwriters will be obligated to purchase all the securities of the series offered if they purchase any of the securities of that series. We may change from time to time any initial public offering price and any discounts or concessions the underwriters allow or reallow or pay to brokers or dealers. We may use underwriters with whom we have a material relationship. We will describe the nature of any such relationship in any prospectus supplement naming any such underwriter. Only underwriters we name in the prospectus supplement are underwriters of the securities offered by the prospectus supplement.

        We may also sell securities directly to one or more purchasers without using underwriters or agents. Underwriters, brokers, dealers and agents that participate in the distribution of the securities may be underwriters as defined in the Securities Act, and any discounts or commissions they receive from us and any profit on their resale of the securities may be treated as underwriting discounts and commissions under the Securities Act. We will identify in the applicable prospectus supplement any underwriters, brokers, dealers or agents and will describe their compensation. We may have agreements with the underwriters, brokers, dealers and agents to indemnify them against specified civil liabilities,

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including liabilities under the Securities Act, or to contribution with respect to payments which they may be required to make in respect thereof. Underwriters, brokers, dealers and agents may engage in transactions with or perform services for us in the ordinary course of their businesses.

        We, and/or the selling security holders, if applicable, may authorize underwriters, brokers, dealers or agents to solicit offers by certain purchasers to purchase the securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. The contracts will be subject only to those conditions set forth in the prospectus supplement, and the prospectus supplement will set forth any commissions we pay for solicitation of these contracts.

        Unless otherwise specified in the applicable prospectus supplement, each class or series of securities will be a new issue with no established trading market, other than our common stock and warrants, which are listed on The NASDAQ Global Select Market. We may elect to list any other class or series of securities on any exchange or market, but we are not obligated to do so. It is possible that one or more underwriters may make a market in a class or series of securities, but the underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We cannot give any assurance as to the liquidity of the trading market for any of the securities.

        Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of these activities at any time.

        Any underwriters who are qualified market makers on The NASDAQ Global Select Market may engage in passive market making transactions in the securities on The NASDAQ Global Select Market in accordance with Rule 103 of Regulation M, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security. If all independent bids are lowered below the passive market maker's bid, however, the passive market maker's bid must then be lowered when certain purchase limits are exceeded.

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LEGAL MATTERS

        Paul Hastings LLP, San Diego, California will pass for us upon the validity of the securities being offered by this prospectus. If the securities are being distributed in an underwritten offering, certain legal matters will be passed upon for the underwriters by counsel identified in the related prospectus supplement.

EXPERTS

        The consolidated financial statements, incorporated in this Prospectus by reference from the Company's Annual Report on Form 10-K, and the effectiveness of Kratos Defense and Security Solutions, Inc.'s internal control over financial reporting have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report, which is incorporated herein by reference. Such consolidated financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

        We are a reporting company and file annual, quarterly and current reports, proxy statements and other information with the SEC. We have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the securities we are offering under this prospectus. This prospectus does not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the securities we are offering under this prospectus, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. You may read and copy the registration statement, as well as our reports, proxy statements and other information, at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. You can request copies of these documents by writing to the SEC and paying a fee for the copying cost. Please call the SEC at 1-800-SEC-0330 for more information about the operation of the Public Reference Room. The SEC maintains an internet site that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC, where our SEC filings are also available. The address of the SEC's website is www.sec.gov. We maintain a website at www.kratosdefense.com. Information contained in or accessible through our website does not constitute a part of this prospectus.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

        The SEC allows us to "incorporate by reference" information that we file with it into this prospectus, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus. Information in this prospectus supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus, while information that we file later with the SEC will automatically update and supersede the information in this prospectus. We incorporate by reference into this registration statement and prospectus the following documents, and any future filings we will make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this prospectus but prior to the termination of the offering of the securities covered by this prospectus (other than current reports or portions thereof furnished under Item 2.02 or Item 7.01 of Form 8-K):

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our annual report on Form 10-K for the year ended December 25, 2016 as filed with the SEC on February 27, 2017;



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our quarterly report on Form 10-Q for the fiscal quarter ended March 26, 2017, filed with the SEC on May 4, 2017, and our quarterly report on Form 10-Q for the fiscal quarter ended June 25, 2017, filed with the SEC on July 27, 2017;



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our current reports on Form 8-K filed with the SEC on January 17, 2017, March 2, 2017, March 7, 2017 and June 6, 2017;



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the portions of our definitive proxy statement on Schedule 14A filed with the SEC on April 14, 2017 that are incorporated by reference into Part III of our Annual Report on Form 10-K for the year ended December 25, 2016; and



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the description of our common stock contained in our Registration Statement on Form 8-A (File No. 000-27231), filed under Section 12(g) of the Exchange Act on September 3, 1999, including any subsequent amendment or report filed for the purpose of amending such description.

        We will provide each person, including any beneficial owner, to whom a prospectus is delivered, a copy of any or all of the information that has been incorporated by reference into this prospectus but not delivered with this prospectus upon written or oral request at no cost to the requester. Requests should be directed to: Kratos Defense & Security Solutions, Inc., Attention: Investor Relations, 4820 Eastgate Mall, San Diego, California, 92121, telephone (858) 812-7300.

        This prospectus, any accompanying prospectus supplement or information incorporated by reference herein or therein, contains summaries of certain agreements that we have filed as exhibits to various SEC filings, as well as certain agreements that we will enter into in connection with the offering of securities covered by any particular accompanying prospectus supplement. The descriptions of these agreements contained in this prospectus, any accompanying prospectus supplement or information incorporated by reference herein or therein do not purport to be complete and are subject to, or qualified in their entirety by reference to, the definitive agreements. Copies of the definitive agreements will be made available without charge to you by making a written or oral request to us.

        Any statement contained herein or in a document incorporated or deemed to be incorporated by reference herein will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained herein, in any other subsequently filed document which also is or is deemed to be incorporated by reference herein or in any accompanying prospectus supplement, modifies or supersedes such statement. Any such statement so modified or superseded will not be deemed, except as so modified and superseded, to constitute a part of this prospectus.

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12,500,000 Shares

Common stock

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Preliminary prospectus supplement

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                  , 2017

   

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