Gun ammunition that derailed Frontier flight at Denver airport belonged to law enforcement, airline says

Lauren Penington, The Denver Post on May 11, 2026

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DENVER — A Frontier Airlines flight deplaned at Denver International Airport on Sunday after an ammunition magazine was discovered on board, according to the airline.

The magazine was found as the Phoenix-bound flight prepared to take off from DIA, Frontier spokesperson Rob Harris said in a statement. The plane was scheduled to depart at 8:08 p.m. Sunday.

“As a matter of precaution, passengers were deplaned and rescreened,” Harris said. “The aircraft also underwent a security sweep with no additional findings.”

Harris said investigators believe the magazine belonged to a law enforcement officer on a previous flight, who likely left it on the plane.

Airport officials responded to the “security incident” to investigate, but no injuries were reported, an unidentified DIA spokesperson stated.

Neither the airport nor the airline has said where or how the gun magazine was discovered, or how it made it onto the plane.

Gun parts — including magazines, clips, bolts and firing pins — are prohibited in carry-on baggage, but may be transported in checked baggage, according to the Transportation Security Administration.

TSA officials did not respond Monday morning to requests for comment.

The delay caused the crew on Frontier flight 4765 to exceed their duty time, and passengers were rebooked on an early Monday flight, Harris said.

That plane took off from DIA just before 6 a.m. Monday and landed in Arizona shortly before 7 a.m., according to flight tracking software FlightAware.

Frontier’s latest security incident comes just days after a pedestrian jumped the Denver airport’s perimeter fence and was killed by a departing plane from that airline. The National Transportation Safety Board was collecting information Sunday to determine if an investigation into the plane’s emergency evacuation after the fatal crash was warranted.

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