Updated

Australia has increased its order for F-35 Joint Strike Fighters by 58 to 72 to be fully operational by 2023 in a declaration of confidence in the troubled stealth war plane.

Prime Minister Tony Abbott said Wednesday he expects the additional 58 U.S. jets, developed by Lockheed Martin Aeronautics Co. will cost 12.4 billion Australian dollars ($11.5 billion).

The F-35 is the Pentagon's most expensive weapons program and has been troubled by schedule delays and cost overruns.

Abbott says he is confident that the cost of about AU$90 million per jet will continue to fall with time.

Australia is a funding partner in developing the F-35 and ordered its first 14 jets in 2009.