An Air Self-Defense Force fighter jet lost its cockpit canopy weighing about 90 kilograms while flying over mountainous areas in southwestern Japan on Sunday, but there were no reports of any injuries or property damage from the incident, according to the Defense Ministry.

The F-2 fighter jet's canopy fell off the aircraft during a scramble mission in response to a possible violation of Japan's airspace by a foreign plane, leaving the pilot exposed to the air in mid-flight, the ministry said.

File photo shows a Japanese Air Self-Defense Force F-2 fighter jet at Tsuiki Air Base in Fukuoka Prefecture in March 2010. (Kyodo)

The Self-Defense Forces have been searching for the canopy, measuring about 150 centimeters in length, 90 cm in width and 80 cm in height, which was believed to have fallen in Asakura, Fukuoka Prefecture.

The fighter made an emergency landing at Tsuiki Air Base in the prefecture, where it is stationed, after the incident took place at around 12:50 p.m. Sunday. Another plane was deployed to replace the F-2 fighter jet for the scramble mission, the ministry said.

The fighter also lost a ladder weighing about 480 grams, with which the aircraft was equipped.

The ASDF decided to conduct inspections of all aircraft and to see if any other parts have fallen from the F-2 fighter.

"We are sorry for causing concern to local residents and the general public," the ministry said. Chief Cabinet Secretary Hirokazu Matsuno said Monday the incident was serious as it could have posed great danger to local people.

Yoshitomo Aoki, an aviation expert, said that such a loss of a canopy is rare but that loosening or defective parts could cause such an incident. But the loss of the canopy would not affect an aircraft's flight functions, he added.

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