Lower-than-expected reliability threatens the future of the F-35 Joint Strike Fighter program, along with doubts as to whether the Pentagon can afford the planned production rate, according to the latest report from the U.S. Government Accountability Office.

The program’s continued failure to develop and test mission software on schedule will also either result in delayed initial operational capability (IOC) dates, or in further reductions to the capability delivered at IOC, the report predicts.

The report released March 24 notes progress in flight sciences testing and in resolving problems with the F-35’s complex helmet-mounted display system and the F-35C carrier variant’s arrester hook. It cites a statement from the JSF Program Office (JSFPO) that the F-35C should be ready for its sea trials in October. However, the report confirms warnings earlier this year from the Pentagon’s director of operational test and evaluation (DOT&E) concerning software development.

By January, the GAO says, the program had verified only half as much of the Block 2B software – the Marine Corps IOC standard – as planned, 13% versus 27%. The GAO endorses the DOT&E’s estimate of a delay as long as 13 months, and recommends a new assessment by the Office of the Secretary of Defense “of the specific capabilities that can be delivered and those that will not likely be delivered” to the services at their different IOC dates. In its response to the GAO report, the DOD agrees to conduct such a risk assessment and to report the outcome to Congress.

The projected cost of the program has been stable since its 2011-12 restructuring, the GAO says, but it sounds an alarm that the total acquisition cost – averaging $12.6 billion per year through 2037, with several years above $15 billion – “does not appear to be achievable in the current fiscal environment,” consuming one-quarter of the Pentagon’s major acquisition funds.

So far, too, no real progress has been made on reducing projected operations and support costs (identified as a major problem in 2011), with average flying hours between failures falling short of projections at this stage. At Aviation Week’s Defense Technology & Requirements conference in Washington earlier this month, JSFPO director Lt. Gen. Chris Bogdan characterized reliability as being “woefully behind the curve” in terms of performance today versus the reliability that was expected at the current cumulative level of flight hours.