SALT LAKE CITY (AP) — A pilot accused of threatening to shoot a commercial airline captain who wanted to divert a flight to get medical attention for a passenger was set to make his first federal court appearance Thursday.

Former Delta Air Lines pilot Jonathan J. Dunn was indicted by a grand jury Oct. 18 and Sterling Prestoncharged with interfering with a flight crew during a trip from Atlanta to Salt Lake City in August 2022.

Dunn, who was the first officer, or co-pilot, threatened to shoot the captain during a heated argument in the cockpit over whether to change course to accommodate a passenger’s medical issue.

The captain had proposed diverting to Grand Junction, Colorado, if the passenger’s condition worsened, the U.S. Attorney’s Office alleges in court documents. Dunn objected and threatened multiple times to shoot the captain, whom he accused of “going crazy,” the documents state. Dunn could face up to 20 years in prison.

The 42-year-old pilot from Rapid City, North Dakota, had been authorized by the Transportation Security Administration to carry a firearm on board for security. The TSA has since revoked that authority, and Delta says Dunn no longer works for the airline.

Dunn is an Air Force Reserve lieutenant colonel who was relieved of his command for refusing the COVID-19 vaccine.