US military officials have allowed F-35 fighter jets to fly again but said the cutting-edge war planes won’t travel to Britain for their planned international debut at the Farnborough airs show.
The Lockheed Martin-made fighter jets, said to be the world’s most expensive weapons project with a price tag of about $400bn (£233bn), have been grounded since a massive failure of a Pratt & Whitney engine on a US Air Force F-35 plane at a Florida air base on 23 June.
The flight clearance, following extensive investigation, comes with restrictions. The radar-evading jets’ engines have to be inspected every three hours and the planes are only allowed to fly at maximum speed of 0.9 Mach under an 18 degrees angle of attack.
With such restrictions in place, it would be impossible for the jets to cross the Atlantic to reach Farnborough, UK, - the place of their scheduled international debut.
"That was a pretty significant limitation in terms of being able to fly them across the Atlantic," said Pentagon spokesman Rear Admiral John Kirby on Tuesday.
The planes, which were to fly along the coast of the US and Canada before reaching Greenland and heading to Europe, would now require more than the originally planned seven hours to complete the journey.
"I can confirm that the Department of Defense in concert with our partners in the UK has decided not to send Marine Corps and UK F-35B aircraft across the Atlantic to participate in the Farnborough air show," Kirby said.
"While we're disappointed that we're not going to be able to participate in the air show, we remain fully committed to the program itself and look forward to future opportunities to showcase its capabilities to allies and to partners."
The jet's failure to appear at a big military air show in Britain last week and its absence from the Farnborough event in southern England have been a blow for US officials and their international partners, who were hoping to highlight the jet's advanced capabilities before potential buyers.
Global orders for the F-35 are expected to exceed 3,000, with Italy, Turkey, Australia and Norway among the US allies planning to purchase the plane.
However, analysts don’t expect the engine troubles would affect purchasing orders.
The inspection of the entire US F-25 fleet suggested the engine issue didn’t seem to be of a systematic nature as no similar problems have been detected in the other 98 engines in service.
US military officials stressed the programme was still in development stages when technical issues and teething problems are meant to be found and corrected.