An Air Force F-15 fighter jet lost its canopy Tuesday morning during routine training off the coast of Okinawa, Japan, the 18th Wing at Kadena Air Base said.
The aircraft landed without incident at Kadena, and there were no injuries.
The cause of the incident was not immediately known, and base safety officials were investigating, according to the wing.
U.S. aircraft based at Kadena regularly train over a vast stretch of ocean to the east of Okinawa.
Last year, a F-15C jet fell into the sea in the Hotel-Hotel training zone, and the pilot safely ejected following mechanical problems.