Amy Butler Washington and Fort Worth

Pentagon officials are satisfied with the pace of flight testing in the nine-nation F-35 Joint Strike Fighter program. However, the initiation of pilot training has once again slipped and prime contractor Lockheed Martin's production pace fell behind owing to a recent strike at the company's Fort Worth final assembly plant.

Despite these hurdles, the project—which has been mired in turmoil for years because of delays in flight testing and multiple multibillion-dollar cost overruns—has “nothing shocking or alarming going on,” says Vice Adm. David Venlet, the Pentagon's F-35 program executive officer. “This is a time of quiet stability for the program.”

Venlet opted not to attend the Farnborough air show, choosing instead to remain in Washington to oversee the program's progress. Senior defense officials from the U.K. will, however, be traveling to Lockheed Martin's Fort Worth facility this month for a ceremony to commemorate acceptance of their first F-35B.

Training for F-35 pilots is slated to begin no earlier than 2013, according to U.S. Air Force Col. Andrew Toth, commander of the 33rd Fighter Wing at Eglin AFB, Fla., the first F-35 training wing. This will mark when the Block 1B software needed for flight training is slated for delivery to Eglin.

Meanwhile, program officials are focused on continuing the pace of flight trials, a key requirement to continue burning down the excessive concurrency between the testing and production phases. In recent months, a major focus has been on preparing for the first F-35 weapons drop, which is slated for the fall, says Venlet.

The test team has already executed load and fit trials for the weapons bay. The aircraft has also been flown in various maneuvers with the weapons bay loaded and doors open to evaluate stresses. This includes carriage of 5,200 lb. of munitions supersonically. Finally, the aircraft has been loaded for external carriage of weapons; though this negates the aircraft's low radar cross section, the external positions offer more flexibility for users to carry various munitions and missiles.

“The lessons are tracking with our predictions,” says Steve O'Bryan, vice president for F-35 business development for Lockheed Martin.