A Japanese F-35A stealth fighter that crashed in the Pacific during an exercise this week did not send an emergency alert, the Air Self-Defense Force said Thursday.

The single-seat jet had an ejector system that would have emitted distress signals if the pilot had got out of the cockpit with a parachute, the ASDF said.

Search operations for the pilot -- a major in his 40s -- by the Self-Defense Forces, the Japan Coast Guard and U.S. forces have been continuing since the airplane disappeared from radar off the coast of northeastern Japan on Tuesday night.

(A Japanese Self-Defense Force vessel and boat searching for a missing F-35A stealth fighter)

The Defense Ministry has concluded the cutting-edge fighter crashed -- citing wreckage from its tails being found in the sea -- making it the world's first such F-35A incident.

The jet disappeared when flying with three other aircraft at distance for an air-to-air combat exercise, about 25 minutes after taking off from Misawa Air Base in Aomori around 7 p.m. Tuesday, according to the ASDF.

Shortly before it dropped off radar, its pilot radioed the other three to say he was about to pull out of the drill, but none then witnessed the plane crash, the ministry said.

Co-developed by nine countries including the United States and Britain, F-35s are produced by U.S. defense company Lockheed Martin Corp.

Before the incident, Japan decided to purchase 105 F-35As from the United States, including those already deployed.