CANBERRA (Dow Jones)--The Lockheed Martin Corp. (LMT) F-35 Joint...

CANBERRA (Dow Jones)--The Lockheed Martin Corp. (LMT) F-35 Joint Strike Fighter aircraft is still the "right choice" for the Australian defense force's next-generation air combat capability, despite being plagued by delivery delays and a costlier-than-expected development, Defense Minister John Faulkner said Friday.

Australia's center-left Labor government last May said it plans to buy up to 100 of the F-35 jet fighters as part of a broader plan to boost defense capability over the next two decades.

Ashton Carter, the top Pentagon official in charge of weapons purchases, told Congress Thursday the average cost of the F-35 Joint Strike Fighter will soar more than 50% above what was projected when its development began nine years ago. The cost blowout occurred despite a restructuring announced by Defense Secretary Robert Gates in February to keep the program on track, including adding 13 months and US$2.8 billion to the development phase.

"As with all highly complex and cutting edge projects, risks are to be expected," Faulkner said in a statement. "Defense will continue to maintain close and regular contact with the U.S. to ensure the success of this vital project."

Australian defense planning has always adopted a "cautious approach" to cost estimates for the F-35 fighter by factoring in significant amounts of contingency funds to deal with cost risks, Faulkner said. He didn't disclose cost estimates, however.

Defense analysts have questioned Australia's need for 100 fighter jets, given that most conflicts Australian defense forces engage in don't require such a sophisticated aircraft.

At a cost of over US$300 billion to develop and buy thousands of airplanes, the Lockheed-led F-35 fighter is the Pentagon's largest-ever contract. It's also crucial to Lockheed's business model and bottom line and is expected to be worth US$15 billion annually in revenue to the company in 2015.