A former Pentagon official testified to Congress that the U.S. government has evidence that "we are not alone in the cosmos," but that a "cabal" of officials is hiding the information.

The official, Luiz Elizondo, is the former head of the Defense Department's Advanced Aerospace Threat Identification Program (AATIP), which was tasked with investigating Unidentified Anomalous Phenomena (UAPs). He and other witnesses testified before the House Oversight Committee.

"Excessive secrecy has lead to grave misdeeds against loyal civil servants, military personnel and the public, all to hide the fact that we are not alone in the cosmos," Elizondo said, later calling the group a "cabal."

"A small cadre within our own government involving the UAP topic has created a culture of suppression and intimidation that I have personally been victim to, along with many of my former colleagues," he continued.

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Elizondo went on to urge Congress to enact legislation protecting whistleblowers who are currently too afraid to come forward about government operations.

"I believe that we as Americans can handle the truth. And I also believe the world deserves the truth," he said.

The hearing is part of a larger effort by lawmakers to investigate UAPs and determine whether elements within the government are unlawfully withholding evidence from Congress.

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One of the key programs involved in the issue is the Pentagon's All-domain Anomaly Resolution Office (AARO).

AARO’s mission is to synchronize efforts across the DoD and other U.S. federal departments and agencies to "detect, identify and attribute objects of interest" in or around military facilities or airspace, which could pose a threat to safety of operations or national security — this includes anomalous, unidentified space, airborne, submerged and trans-medium objects.

The Pentagon says the program has not uncovered any evidence that UAPs have an extra-terrestrial origin.

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Dr. Tim Gallaudet, a retired U.S. Navy rear admiral, also testified at Wednesday's hearing. He recounted an incident where personnel aboard the USS Theodore Roosevelt aircraft carrier had a run-in with UAPs during a military exercise.

"During this exercise, I received an email on the Navy’s secure network from the operations officer of Fleet Forces Command. The email was addressed to all subordinate commanders, and the subject line read in all capital letters: URGENT SAFETY OF FLIGHT ISSUE. The text of the email was brief but alarming, with words to the effect: ‘If any of you know what these are, tell me ASAP. We are having multiple near-midair collisions, and if we do not resolve it soon, we will have to shut down the exercise,'" Gallaudet said.

"Attached to the email was what is now known as the "Go Fast" video, captured on the forward-looking infrared sensor onboard one of the Navy F/A-18 aircraft participating in the exercise," he added.

"The very next day, the email disappeared from my account and those of the other recipients without explanation. Moreover, the Commander of Fleet Forces and his operations officer never discussed the incident again," he continued.

A third witness, journalist Michael Shellenberger, says sources within the Pentagon assert the existence of an Unacknowledged Special Access Program (USAP) known as "Immaculate Constellation."

He says the sources told him that the program consolidates information on UAPs that has been gathered by the military.

"A source warned that simply printing the name ‘Immaculate Constellation’ could trigger government surveillance of me under the Foreign Intelligence Surveillance Act (FISA) of whoever publishes it," Shellenberger said. "'They won’t comment on it, but talking about it will put you in the danger zone,' I was told. 'They enforce the secrecy with a lot of vigor.'"