Former Delta pilot Jonathan Dunn's threat to shoot his captain while the plane was in the air was "a misunderstanding," according to Dunn's lawyer. 

But prosecutors described the heated argument during a 2022 flight from Atlanta to Salt Lake City as a "grave offense."

The two sides sparred in a Utah courtroom Thursday during Dunn's first federal court appearance since his October 2023 indictment for threatening his co-pilot after he suggested diverting the flight for a passenger's medical emergency.

Dunn allegedly responded with a slew of menacing remarks, and the unnamed co-pilot thought Dunn would use his gun to "relieve" him of command of the aircraft, according to court documents. 

FORMER DELTA PILOT INDICTED AFTER ALLEGEDLY THREATENING TO SHOOT CAPTAIN DURING FLIGHT

Prior to this incident, the Transportation Security Administration authorized Dunn to carry a gun on board, a right that has since been revoked. 

The midair altercation also cost Dunn his job with Delta, which said he is no longer with the airline after a grand jury indicted him on a federal charge of interfering with a flight crew.

If he's convicted, Dunn could face up to 20 years in prison. The trial date has been tentatively set for March 20. 

ALASKA AIRLINES OFF-DUTY PILOT PLEADS NOT GUILTY AFTER ALLEGEDLY TRYING TO CUT ENGINES 

Dunn admitted to making remarks but said they were intended as a joke, according to a report by the Associated Press, citing new court documents. 

The former pilot's lawyer, John Huber, said after the court appearance his client doesn't have a criminal history and shouldn't be considered dangerous. 

With that said, Dunn seemed to recognize in hindsight the gravity of his actions, telling Delta officials, "This could have been much worse. In hindsight, if I had been threatened, I would not be able to operate," the Associated Press reported. 

Dunn and his co-pilot's heated exchange on the last leg of a three-day, cross-country rotation that the two completed together, according to the Associated Press. 

The captain said Dunn questioned his decisions throughout the trip and attempted what he called a "right-seat captain."

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Dunn is an Air Force Reserve lieutenant colonel who was demoted from his previous position for refusing the COVID-19 vaccine. 

The Air Force suspended his access to sensitive information and to the air operations center because of the mid-flight altercation, a spokesperson told the Associated Press.