Search and rescue teams found wreckage from a Japanese F-35 stealth fighter that crashed over the Pacific Ocean close to northern Japan, but the pilot remains missing, authorities said today.

The aircraft, less than one-year-old, was the first F-35 to be assembled in Japan and was only in the air for 28 minutes yesterday, a defence official said.

It is only the second F-35 to crash in the two-decades it has been flying.

The advanced, single-seat jet was flying about 135 km (84 miles) east of the Misawa air base in Aomori Prefecture at about 7:27 pm (1027 GMT) yesterday when it disappeared from radar, the Air Self Defense Force said.

"We recovered the wreckage and determined it was from the F-35," a spokesman for the Air Self Defence Force (ASDF) said, adding that the pilot of the aircraft was still missing.

The aircraft was at the front of a group of four planes out for training manouvres when it sent an "aborting practice" signal and then disappeared from the radar, Defence Minister Takeshi Iwaya told reporters.

"We'll need to cooperate with the US forces and I believe arrangements are being made for this," Iwaya said, adding the priority was on determining the cause of the accident.

Japan has a total of 13 F-35s, including the one that crashed. The crashed aircraft was the fifth F-35 delivered to the ASDF, but the first assembled by Mitsubishi Heavy Industries in Japan, a second ASDF official told Reuters.

The previous four aircraft had been used for training in the United States before being brought to Japan, the defence official said.

A representative for Mitsubishi Heavy Industries said the company had no immediate comment. Mitsubishi Heavy Industries Ltd assembles the aircraft at a plant near Nagoya in central Japan. Each costs around $100 million, slightly more than the cost of buying a fully assembled plane.

The aircraft had been in the air for 28 minutes when contact was lost, the official said. The pilot had 3,200 hours of flight time, with 60 hours on the F-35, the official said.

The aircraft crashed in waters that reach a depth of around 1,500 metres, making recovery difficult, the official said.

ONLY SECOND F35 TO CRASH

The aircraft was less than a year old and was delivered to the ASDF in May last year, the ASDF spokesman said. Japan's first squadron of F-35s has just become operational at Misawa and the government plans to buy 87 of the stealth fighters to modernise its air defences as China's military power grows.

The crash marks only the second time an F-35 has gone down since the plane began flying almost two decades ago. It was also the first crash of an A version of the fifth-generation fighter, which is designed to penetrate enemy defences by evading radar detection.

Lockheed Martin, which manufactures the aircraft, said it was standing by to support the Japanese Air Self Defense Force as needed. The Pentagon said it was monitoring the situation.

A US military short take off and landing (STOVL) F-35B crashed near the Marine Corps Air Station Beaufort in South Carolina in September prompting a temporary grounding of the aircraft. Lockheed Martin also makes a C version of the fighter designed to operate off carriers.

Japan's new F-35s will include 18 short take off and vertical landing (STOVL) B variants that planners want to deploy on its islands along the edge of the East China Sea.