A Japan Air Self-Defense Force aircraft made an emergency landing on Thursday after a cockpit window suddenly opened about 800 meters above waters off Sado Island in central Japan.
The C2 transport aircraft landed at Niigata Airport after the window on the left side of the cockpit slid open during a training flight.
The ASDF said none of the eight crewmembers were injured, and the window did not fall off the aircraft.
Investigations have found that the window opened at around 4:55 p.m. while the plane was flying north of Sado Island in the Sea of Japan at an altitude of about 800 meters. It had taken off from Iruma Air Base near Tokyo.
The ASDF says the window is designed to be opened and shut manually and basically locked during flight.
The C2 transport aircraft was parked at Niigata Airport early on Friday morning. The ASDF says it is uncertain when the plane can resume operation.