A decision to start production of Lockheed Martin Corp's F-35 fighter jet before it was fully tested has driven up the $396 billion cost of the troubled project and increased risks, the U.S. general heading development of the warplane has said.
The head of the Pentagon's F-35 program office, Lieutenant General Chris Bogdan, told Australian Broadcasting Corporation (ABC) television that major challenges had been created by a production and test approach known as "concurrency".
"A large amount of concurrency, that is, beginning production long before your design is stable and long before you've found problems in tests, creates downstream issues where now you have to go back and retrofit airplanes and make sure the production line has those fixes in them," Bogdan told ABC's Four Corners program late on Monday.
"That drives complexity and cost. Let's make no mistake about it. This program still has risks, technical risks, it has cost issues, it has problems we'll have to fix in the future," he said in his first interview on the problem-plagued F-35.
Australia's government is looking at buying 24 more Boeing F/A-18 Super Hornets amid continuing delays and setbacks in the Joint Strike Fighter project, which is the costliest program in Pentagon procurement history.
That means Australia could buy fewer than the 100 F-35s originally planned, echoing warnings from Canada that it could also look to other options for its future jet fighters. The Netherlands and Italy have also cut back orders.
The F-35 has been co-developed by the United States and eight foreign partners - Britain, Italy, Netherlands, Turkey, Canada, Australia, Denmark, and Norway. Purchase contracts have also been signed by Israel and Japan.
Bogdan, who will travel to Australia in coming weeks for talks on the F-35 Lightning II, said the aircraft was ironically unable to fly within 40 km (25 miles) of a lightning storm because its fuel tanks could ignite.
"Will this problem occur in the future? No, because we have the known fixes for it and we will fix it," he said.
The aircraft was developed as a replacement for several different types of U.S. warplanes.
A spokeswoman for Australian Defence Minister Stephen Smith said a government decision last year to defer orders of its first squadron of F-35s would limit Canberra's exposure to the spiraling cost of the project.
Australia is due to decide at the end of this year on the timing of its next order of 12 F-35s while it considers options to replace Classic F/A-18 fighter jets. Canberra's fleet of 71 F/A-18s entered service between 1985 and 1990 and were due to retire by around 2020.
Australia also has 24 of the new generation F/A-18F Super Hornets, which entered service in 2010 and 2011, 12 of which have been upgraded with sophisticated U.S. jamming equipment.