The Pentagon's most expensive weapons program ever, the F-35 warplane, is cleared for takeoff again. The limited flight clearance, approved by Navy and Air Force officials Monday, allows the aircraft to fly with an engine inspection regimen and restricted flight envelope following the fleet's grounding after an engine fire last month. Defense Department spokesman Mark Wright said in a statement Tuesday the restrictions would "remain in effect until the root cause of the June 23 engine mishap is identified and corrected." It had been hoped that the stealth fighter would be able to make an appearance at the famed Farnborough air show, under way now, but Pentagon spokesman Rear Adm. John Kirby said Tuesday afternoon that won't happen. "The Department of Defense, in concert with our partners in the U.K., has decided not to send Marine Corps and U.K. F-35B aircraft across the Atlantic to participate in the Farnborough air show," he told reporters.  "This decision was reached after a consultation with senior leaders and airworthiness authorities, despite the decision by airworthiness authorities to clear the aircraft to return to flight -- to limited flight." The 2014 Farnborough International Airshow began Monday, and runs through July 20 in Farnborough, England.  The opening day brought $42 billion of orders and commitments for commercial aircraft and engines, according to a statement from the show's organizers. The F-35 was developed at a cost of nearly $400 billion so far and beset for years by cost overruns and delays. The so-called Joint Strike Fighter was temporarily grounded following a fire on the runway at Eglin Air Force Base in Florida. No one was hurt. Engine maker Pratt & Whitney worked with Air Force investigators to inspect all engines in the fleet. "We have great confidence in the F135 engine powering the F-35, and we have worked very closely with DoD and the Services to return the aircraft to flying status," Matthew Bates, communications manager for Pratt & Whitney Military Engines, said in a statement Tuesday. The F-35's lead contractor, Lockheed Martin, which is producing variants of the plane for the U.S. Navy, Marines and Air Force,  also worked with investigators following the fleet's grounding. F-35 future . The Pentagon wants more than 2,400 of the fighter jets ultimately, while hundreds more are expected over time to go to allies such as South Korea, Japan and Australia. More than 100 planes have been built so far, most for testing, but the program is still in its development and training phases. The military says the stealthy fighter will be "the most affordable, lethal, supportable and survivable aircraft ever to be used" by so many services worldwide. But its production has been controversial for its soaring cost history -- the price tag has nearly doubled from early estimates, to $135 million per unit as of last year, according to a U.S. Government Accountability Office report in March -- as well as its schedule, software and other setbacks. Test flights began in 2007. While all models have been grounded in the past for various problems, the version for the Marines, the F-35B, has had more issues. Experts say that's mainly due to its design for shorter takeoffs and vertical landings. Richard Aboulafia, a Teal Group analyst, said earlier this month that every component of the F-35 overall "is pushing the frontiers of technology" as engineers combine extraordinary engine power with a lighter weight design. He said the program has made gradual progress in recent years where glitches get resolved pretty quickly compared with 18 to 24 months ago, when setbacks seemed to come one right after another. "It's a tremendously complex project," he said, adding that cost issues remain a concern.
The F-35 won't participate in the Farnborough air show, Pentagon spokesman says .
The return to flight order is a limited flight clearance .
The F-35 fleet was grounded after an engine fire in June .
Pratt & Whitney, Lockheed Martin working with investigators to find cause of fire .
The Pentagon's most expensive weapons program ever, the F-35 warplane, is cleared for takeoff again. The limited flight clearance, approved by Navy and Air Force officials Monday, allows the aircraft to fly with an engine inspection regimen and restricted flight envelope following the fleet's grounding after an engine fire last month. Defense Department spokesman Mark Wright said in a statement Tuesday the restrictions would "remain in effect until the root cause of the June 23 engine mishap is identified and corrected." It had been hoped that the stealth fighter would be able to make an appearance at the famed Farnborough air show, under way now, but Pentagon spokesman Rear Adm. John Kirby said Tuesday afternoon that won't happen. "The Department of Defense, in concert with our partners in the U.K., has decided not to send Marine Corps and U.K. F-35B aircraft across the Atlantic to participate in the Farnborough air show," he told reporters.  "This decision was reached after a consultation with senior leaders and airworthiness authorities, despite the decision by airworthiness authorities to clear the aircraft to return to flight -- to limited flight." The 2014 Farnborough International Airshow began Monday, and runs through July 20 in Farnborough, England.  The opening day brought $42 billion of orders and commitments for commercial aircraft and engines, according to a statement from the show's organizers. The F-35 was developed at a cost of nearly $400 billion so far and beset for years by cost overruns and delays. The so-called Joint Strike Fighter was temporarily grounded following a fire on the runway at Eglin Air Force Base in Florida. No one was hurt. Engine maker Pratt & Whitney worked with Air Force investigators to inspect all engines in the fleet. "We have great confidence in the F135 engine powering the F-35, and we have worked very closely with DoD and the Services to return the aircraft to flying status," Matthew Bates, communications manager for Pratt & Whitney Military Engines, said in a statement Tuesday. The F-35's lead contractor, Lockheed Martin, which is producing variants of the plane for the U.S. Navy, Marines and Air Force,  also worked with investigators following the fleet's grounding. F-35 future . The Pentagon wants more than 2,400 of the fighter jets ultimately, while hundreds more are expected over time to go to allies such as South Korea, Japan and Australia. More than 100 planes have been built so far, most for testing, but the program is still in its development and training phases. The military says the stealthy fighter will be "the most affordable, lethal, supportable and survivable aircraft ever to be used" by so many services worldwide. But its production has been controversial for its soaring cost history -- the price tag has nearly doubled from early estimates, to $135 million per unit as of last year, according to a U.S. Government Accountability Office report in March -- as well as its schedule, software and other setbacks. Test flights began in 2007. While all models have been grounded in the past for various problems, the version for the Marines, the F-35B, has had more issues. Experts say that's mainly due to its design for shorter takeoffs and vertical landings. Richard Aboulafia, a Teal Group analyst, said earlier this month that every component of the F-35 overall "is pushing the frontiers of technology" as engineers combine extraordinary engine power with a lighter weight design. He said the program has made gradual progress in recent years where glitches get resolved pretty quickly compared with 18 to 24 months ago, when setbacks seemed to come one right after another. "It's a tremendously complex project," he said, adding that cost issues remain a concern.
again. The limited flight clearance, approved by fleet's grounding after an engine fire last Atlantic to participate in the Farnborough air the aircraft to return to flight -- to limited was hurt. Engine maker Pratt & Whitney worked The F-35's lead contractor, Lockheed Martin, with investigators following the fleet's a concern.