Air Force Lieutenant General Chris Bogdan, the Pentagon's F-35 program chief, told reporters the Air Force was counting on training experienced A-10 mechanics to help reach the total 1,100 mechanics needed to declare that the F-35 had reached "initial operational capability" or IOC.

But Congress is blocking the Air Force's plan to retire the A-10 aircraft, which means that those mechanics will be needed to maintain the older A-10 fleet, he said, adding that it would take nine to 12 months longer to train new mechanics to service the F-35 than retraining an already experienced mechanic.

Bogdan said there was also a risk of a brief delay in the July 1, 2015, target date for the Marine Corp's IOC due to a 45- to 50-day delay in flight testing caused by an engine failure that sparked a fleetwide grounding this summer, and the resulting lingering flight restrictions.

Pentagon acquisition chief Frank Kendall this week told Aviation Week that the Marine Corps could miss its target date, but Commandant General James Amos told Reuters before his retirement on Oct. 17 he still viewed that target as "doable."

Bogdan said he was concerned about the possible delay and was still hoping to avoid it, but did not expect the target date to slip by more than a couple of weeks, if at all.

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