This year’s second grounding of Lockheed Martin Corp’s F-35 warplane, plus looming U.S. defence cuts, will complicate a push this week by Lockheed and U.S. officials to convince Australian lawmakers and generals to stick to a plan to buy 100 of the jets.

Australia, a close American ally, is considering doubling its fleet of 24 Boeing Co F/A-18 Super Hornets amid delays and setbacks in Lockheed’s $396 billion F-35 project.

That means Canberra could buy far fewer F-35s than initially planned, at a time when Canada is also rethinking its plans to make the F-35 - also known as the Joint Strike Fighter (JSF) - its future frontline warplane.

U.S. Lieutenant General Christopher Bogdan, the Pentagon program chief for the F-35, said the grounding over a crack found in a test aircraft engine would not delay delivery of the most expensive combat aircraft in history.

“It is not unusual in development programs for these things to happen,” Bogdan told reporters at an airshow in the Australian city of Melbourne, where the futuristic jet will draw attention from potential customers in Asia.

“Don’t be shocked in the future if we find other things wrong with the airplane that will result in us doing the same thing.”

All flights by the 51 F-35 fighter planes were suspended on Friday after a routine inspection revealed a crack on a turbine blade in the jet engine of a test aircraft in California.