London (AFP) - The first international appearance of the F-35 fighter in Britain on Friday has been cancelled as the fleet remains grounded in the United States, in an embarrassing setback for the costly programme.
The stealth fighter jet had been due to take part in a military aviation display, the Royal International Air Tattoo, ahead of its formal presentation at the Farnborough International Air Show next week.
Lorraine Martin, general manager of the F-35 programme at US defence firm Lockheed Martin, said she still hoped the planes would make it to the air show in Britain.
"It's not in my hands but I'm hopeful it will be the case," she told reporters at the Fairford airbase in south-west England, where the military display was due to start on Friday.
"As soon as they arrive we will be part of as much as possible of the flying schedule."
Both the US Air Force and Navy last week ordered a halt to all F-35 flights following a June 23 engine fire on one of the planes, which at $400 billion (300 billion euros) is most expensive weapons project in US history.
"We still have a safety investigation going on," said Lieutenant General Chris Bogdan, the US Department of Defense official in charge of the programme, adding that "we haven't learned enough yet".
He insisted however that "the airplane is still in development" and such problems were not rare.
Britain has invested heavily in the jets, which are to be used on its new generation of aircraft carriers.
Officials had viewed the July 14-20 Farnborough Show as a promising opportunity to show off the new plane before a global audience of potential buyers.
Missing it would be yet another setback for the programme, which has been plagued by repeated delays and cost overruns.
US Defense Secretary Chuck Hagel was due to visit the Eglin base in Florida on Thursday where the engine fire took place to demonstrate the United States' continuing commitment.
Four F-35Bs, the vertical take-off version designed for the US Marine Corps, are due to feature at Farnborough, including one aircraft belonging to Britain that is undergoing tests in the United States.
"If the F-35 doesn't make it to the show it's quite embarrassing. It will jeopardise the timing of export orders," said Richard Aboulafia, an analyst with Teal Group.
"But assuming there's no major problems here, we aren't expecting a serious blow to the programme."