The Defense Ministry said that search operations were continuing Feb. 1 for two pilots of an Air Self-Defense Force F-15 fighter jet that disappeared from radar the previous night over the Sea of Japan.
It said on January 31 that the wreckage had been found but there was still no trace of the missing pair.
The two-seater aircraft swerved sharply to the right immediately after it took off from the ASDF's Komatsu Air Base in Komatsu, Ishikawa Prefecture, but did not activate an emergency signal, ministry sources said.
They concluded that the aircraft developed an engine problem and went into a nose dive.
It took off from the base at 5: 30 p.m. on January 31 to fly west-southwest on a night-time flight training mission. It was flown by two male pilots, one in the front of the cockpit and the other in the back seat.
The training was to simulate night-time fighter interception in the event of an enemy invasion. Ministry officials said aircraft vanished from radar about 5 kilometers west-northwest of the base while heading to airspace for a training area about 20 km north of the base.
It tilted to the right while ascending to change course and then appeared to lose thrust and fell steeply, the ministry said.
The incident occurred less than a minute after takeoff.
The Japan Coast Guard received an emergency call around 5: 30 p.m. on January 31 from a private citizen who saw light in the Wreckage identified as part of an outer panel and life-saving equipment aboard the aircraft. It was spotted around 7: 10 p.m. in the vicinity where it disappeared and was later retrieved.
The two pilots would have worn life-saving gear that is designed to automatically activate a radio signal in the event of an emergency.
Officials said the equipment was most likely wrecked on impact or sank.
The search operation involves three helicopters from the ASDF and the Maritime SDF, an ASDF aircraft, five MSDF ships and three coast guard patrol vessels.
As of the morning of February 1, no trace of the two pilots had been found.
Defense Minister Nobuo Kishi told the ASDF to conduct an immediate emergency safety inspection of all its aircraft, so we will continue to gather information about what happened and do everything in our power to rescue the pair.
The crashed jet, an F 15 DJ type, measures 19.4 meters long, 13.1 meters wide and 5.6 meters high. Its maximum velocity is about Mach 2.5.
Its mission is to try to intercept a foreign aircraft that has violated Japan's airspace.
The tactical fighters training group is located at the Komatsu base.
The group of highly skilled veteran elite pilots plays an enemy role in training exercises with other troop units nationwide and goes by the nickname aggressor. In July 2011 an F-15 fighter jet belonging to the ASDF's Naha Air Base disappeared from radar at sea about 180 km northwest of the city of Naha, the prefectural capital of Okinawa.
Wreckage from the aircraft was found later.
In April 2019, a single-seated F-35 A fighter jet from the ASDF's Misawa Air Base in Aomori Prefecture went missing over the Pacific Ocean about 135 km east of the base.
Aircraft wreckage found in the surrounding area suggested it had crashed, officials said.