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The senators questioned whether lifting the probation was premature, given the F-35’s problems during testing such as the design of the plane’s tailhook for aircraft carrier landings and its helmet-imaging system.

Col. Kevin Killea, head of aviation requirements for the Marine Corps Headquarters, said that such problems have either been corrected, or have been addressed with a temporary fix until a permanent solution can be implemented.

Mr. McCain last week said he was encouraged the program is moving in the right direction.

“After several major restructuring efforts over the last two years the Government Accountability Office recently found for the first time in the program’s history that the program is finally set up to produce more achievable and predictable outcomes,” he said at the Marine Corps‘ unveiling of the F-35B in Yuma.