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US F-35 fighters cleared to fly after engine fire

The US fleet of troubled F-35 fighters has been cleared to fly again but investigators are still uncertain what caused an engine fire on one of the aircraft, the Pentagon said Tuesday.

WASHINGTON: The US fleet of troubled F-35 fighters has been cleared to fly again but investigators are still uncertain what caused an engine fire on one of the aircraft, the Pentagon said Tuesday.

US Navy and Air Force aviation authorities lifted a ban on flights after having grounded the costly plane and left the door open to the Joint Strike Fighter taking part in the high-profile Farnborough air show in Britain.

The decision gave only a partial green light to the F-35 and ordered a schedule of inspections and flight restrictions.

"This is a limited flight clearance that includes an engine inspection regimen and a restricted flight envelope which will remain in effect until the root cause of the June 23 engine mishap is identified and corrected," Pentagon press secretary Rear Admiral John kirby said in a statement.

"We remain hopeful that the F-35 can make an appearance at the Farnborough air show," he said.

No final decision had been made on whether the plane would make its planned international debut at the Farnborough event, said Kirby, adding that "safety remains the overriding priority."

The new warplane, touted as a technical wonder that will form the core of America's future fighter fleet, already missed a British military aviation event over the weekend and the first day of the Farnborough show, which began on Monday and runs through Sunday.

At nearly $400 billion, the F-35 is the most expensive weapons program in US history and officials are eager to reassure foreign partners and potential customers that the warplane remains on course.

But the project has suffered one technical setback after another and the latest problem has turned into a public relations headache, just as the Pentagon planned to stage the plane's coming-out-party at Farnborough.

US officials chose the Farnborough air show as a way of showcasing the plane in a country that committed to the project early and has invested heavily in the fighter.

Apart from the United States and Britain, seven countries are taking part in the program: Australia, Canada, Denmark, Italy, the Netherlands, Norway and Turkey.

Israel has expressed an interest in the Joint Strike Fighter, as has Japan, South Korea and Singapore.

On June 23, an engine caught fire on a F-35 as it was about to take off from Eglin Air Force Base in Florida. The pilot managed to escape unharmed and investigators are still trying to get to the bottom of the incident.

The Pentagon's top weapons buyer, Frank Kendall, has said that an inspection of the whole fleet of aircraft indicates the fire was an isolated incident and not part of a broader, systemic problem.

Critics of the plane, which is years behind schedule, have seized on the latest problem as proof that the project is deeply flawed.

One US lawmaker, Jim Moran of Virginia, demanded a briefing on the probe into the fire and said the incident "should raise serious concerns about the viability of the program."

Pentagon officials acknowledge a main cause of the plane's troubles was a decision to start building the jet before testing was finished. As a result, bugs and other technical glitches have forced repeated repairs and redesign work, slowing down production.

Officials and industry executives insist the plane promises to become the ultimate stealth fighter jet, able to evade enemy radar while flying at supersonic speeds. But the plane so far has yet to achieve the level of performance and reliability expected.

Fresh questions about the F-35 program came as US senators prepared Tuesday to debate military spending proposals for the Joint Strike Fighter for the next fiscal year. The House of Representatives has backed funding for four more aircraft than the Pentagon requested.

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