YOKOSUKA NAVAL BASE, Japan — The Pentagon’s $396 billion program to develop the F-35 Joint Strike Fighter has made progress but still faces long-term affordability concerns, according to a General Accountability Office report released Monday.

The multi-service fighter jet program met seven of 10 management objectives in 2012, including goals on cost efficiency and training.

The objectives that went unmet were caused by a one-month delay on a design review, 10 fewer jets delivered than planned and lack of compliance by contractor Lockheed Martin on a set of Defense Department contracting processes.

Despite those shortcomings, the findings represent a comparatively positive assessment of the F-35 since the GAO was directed by Congress to issue annual reports in 2010.

“Overall, the F-35 Joint Strike Fighter program is now moving in the right direction after a long, expensive and arduous learning process,” the report stated.

The Defense Department began the F-35 program in 2001, but made revisions in 2003, 2007, 2010 and 2012 after performance problems, delays and cost overruns.

The original 2001 estimates of 2,852 planes at a cost of $233 million have turned into about 400 fewer planes for 70 percent more money, and over a longer period of time.

Decreasing labor hours and a quickening delivery pace are improving cost efficiency, according to the report. Nevertheless, the program is slated to cost $12.6 billion per year through 2037.

That number could still change, since the bulk of development testing for the F-35 lies ahead. The Pentagon will then have to grapple with how to fund maintenance for the most expensive fighter plane in history.

“Once acquired, the current forecasts of life cycle sustainment costs for the F-35 fleet are considered unaffordable by defense officials,” according to the report. “Efforts are under way to try and lower annual operating and support costs.”

Despite setbacks, such as a crack found in an Edwards Air Force base jet turbine blade that caused the Pentagon to briefly ground the F-35 fleet in February, the GAO report states that field testing has improved.

Both the Navy’s F-35C carrier-based model and the Marine Corps’ F-35B vertical take-off model are now ahead of schedule on test flights, according to the report.

The Air Force’s model did not reach that goal due to problems with the air refueling system; however, it conducted its high angle of attack, initial weapons separation and engine air start testing.

The Defense Department has acquired 52 F-35 jets to date, 14 of which are test models, according to the GAO. Several international allies, including Japan, plan to acquire variants of the aircraft.

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