LONDON — The failure of the Joint Strike Fighter to travel to England this week for a premier air show heaped further embarrassment on its developers as they try to convince skeptics that the $400 billion program was a price worth paying.The plane couldn't cross the Atlantic to be gazed at by industry experts at the Farnborough Airshow in southern England, as experts try to sort out the causes of a recent engine fire — fueling the ammunition of critics who have questioned whether there is a bigger and more systemic problem with the fighter jet."It's another hiccup in a series of them," said Winslow T. Wheeler, a critic of the program and director of the Straus Military Reform Project.Wheeler said the complexity of the plane, which is designed to combine stealth, maneuverability and attack capabilities in a single aircraft, makes it vulnerable to multiple troubles. The only thing different now was that the plane was getting close attention because of the airshow, which alternates every year between Paris and Farnborough.He said the plane's failure to make it to this year's show and the ensuing negative publicity will make people wonder about the cost of the fighter, now estimated at $80 million each."The politicians are that much more agitated," he said.The F-35B Lightning II, the new multirole fighter, was supposed to be the centerpiece at Farnborough, the debutante to watch at the premiere event in aviation.But after days of pushing the deadline to announce whether it would come as planned, the Defense Department was forced Tuesday to announce it wouldn't come. But it couldn't make the trip because in light of the fire, the engines had to be inspected every three hours, making a flight across the Atlantic impractical.The extent of the dashed marketing for the F-35 was clear Wednesday, with the exhibit space that had been earmarked for the plane empty except for a few posters and video screens showing the plane.One poster dubiously asked "Need a lift?"The United States is supposed to build almost 2,500 of the planes. Nine partner countries, including the U.K., Denmark and Italy, are involved in the plane's production, too.Industry representatives at the show were just plain disappointed at its absence.This, after all, is where the plane would have found its most avid audience — people who would really understand what it can do."I'm disappointed," said Larbi Ouchelouche, the project manager of SPEEL Praha Ltd., a company that makes the flight recorders known as black boxes. "We were really looking forward to seeing it."This is also the group that best understands how complicated it can be to get an all-new aircraft through testing.Robert Whitehouse, the business development director for aerospace, defense and security at Tekever, said testing planes never moves in a straight line."Safety comes first," he said. "People wanted to see it. But they will understand."