Problems in testing critical computer software could add more than a year to the Joint Strike Fighter program, the US government's auditor says.
This is the software which would allow the JSF to go to war and would impact training on Australia's first two aircraft, set for delivery in the US later this year.
However, problems should be fixed by the time Australia takes delivery of larger numbers of aircraft to achieve initial operational capability in 2020.
The US Government Accountability Office says holdups in testing of critical mission system software could delay delivery of expected warfighting capabilities by up to 13 months.
That will most directly affect the US Marine Corps, which plans to field its first operational squadron in July 2015.
It's in line with a warning delivered in Canberra this month by Lieutenant General Chris Bogdan, head of the Pentagon's JSF program office.
He said much of the program was proceeding well but he remained concerned about development of JSF's complex software, especially its ability to receive and disseminate data to and from satellites, airborne warning aircraft, ground radars and other aircraft.
Australia plans to buy up to 100 JSF aircraft at a cost of some $16 billion.
The GAO does deliver some good news.
Of the three JSF variants, the conventional take-off and landing (CTOL) version, which Australia is buying, is proving most reliable, though not yet as reliable as planned.
JSF is also getting cheaper as increasing production gives economies of scale.
Projections, based on US Department of Defense data, point to a unit cost of $US83.4 million ($A91.25 million) for CTOL aircraft procured in 2019, when Australia's next aircraft will be coming off the production line.
