WASHINGTON — A U.S. Air Force F-35 deployed to Kadena Air Base in Japan lost a panel during a Nov. 30 training flight over the Pacific Ocean, the service confirmed Monday.

An aircraft panel measuring approximately 12 inches by 24 inches dropped from an F-35A sometime during a “routine training mission” about 65 miles east of Okinawa, according to a news release from 18th Wing Public Affairs at Kadena Air Base.

“The item was discovered missing by the pilot’s wingman as the fighter jets were coming in for landing” and was later confirmed missing after a post-flight inspection, the release stated. Because inspections are also done prior to takeoff, it is thought that the panel fell off sometime during the flight.

Although the Air Force had not commented on or confirmed the mishap prior to Monday, the Japanese media has been aware of the incident since it occurred on Nov. 30. Nippon News Network featured footage of the F-35A showing the missing panel, which was then shared by aviation enthusiasts across Twitter.

It was not clear whether any attempt will be made to recover the missing panel, or whether the loss of part of the F-35’s structure causes any concerns from a safety or technology security standpoint.

Twelve F-35A conventional takeoff and landing models from the 34th Fighter Squadron at Hill Air Force Base, Utah, arrived at Kadena in November for a six months stint in the Asia-Pacific, the first time the A-variant has deployed to the region since it became operational in August 2016. The deployment is being supported by more than 300 pilots, maintainers and other personnel.

Unlike the F-35A’s much-hyped deployment to Europe earlier this year, the joint strike fighter has kept a low profile since coming to Japan. Kyodo News reported in early November that one jet had made an “emergency landing,” after which the aircraft was examined by firefighters. The Air Force called it a “precautionary landing” and said there was no risk of injury or property damage due to the event.

The Air Force provided few details about the purpose of the training mission that caused the loss of the aircraft panel.

“As a matter of policy, we do not discuss the details or specifics of our training or operations,” public affairs said in its statement.