Rescuers were searching for the pilot of a U.S. fighter jet missing over the Adriatic Sea on Monday, the U.S. military announced.

Controllers lost contact with the F-16 around 8 p.m. Monday (2 p.m. ET) while the jet was on a training flight, the U.S. Air Force reported. The single pilot's condition was not immediately known, the service said.

The jet was based at Aviano Air Base, a key NATO installation in northern Italy.