Japanese defense officials say a search is underway for a fighter jet after it disappeared from radar during a flight exercise in northern Japan.

The Air Self-Defense Force says the F-35A stealth jet went missing Tuesday while flying off the eastern coast of Aomori. It says the plane disappeared from radar about half an hour after taking off from the Misawa air base with three other F-35As for a flight exercise.

Defense Minister Takeshi Iwaya told reporters that a search and rescue operation was underway for the missing jet and its pilot. The cause of the mishap was not immediately known.

Iwaya says 12 other F-35s at the Misawa base will be grounded.

Japan plans to buy 147 U.S.-made F-35s, most of them F-35As, over the next decade.