The Chief of the Royal Australian Air Force has launched a strident defence of the controversial multi-billion-dollar Joint Strike Fighter program, following recent criticisms from former Defence Force members.

In recent weeks, some former ADF personnel and JSF program employees have put forward concerns to a Senate inquiry looking into the massive JSF purchase.

Defence Force officials have told a Senate Estimates hearing the total budget for the F-35A project was $17 billion.

Speaking during the RAAF Air Power Conference in Canberra, Air Marshal Leo Davies conceded the JSF program had its problems, but insisted the F-35 aircraft was still the right choice for Australia.

"I have absolutely no reservations, zero reservations, about the decision for Joint Strike Fighter being the Classic Hornet replacement for Australia," he said.

"I do have some elements of the program that we need to keep an eye on, they need to mature yet."

Air Marshal Davies said the Senate inquiry examining Australia's JSF acquisition had not uncovered any new problems.

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"There are proper questions about understanding its maturity; I think it's a very fair question to ask do we think we understand the aeroplane well enough to give guarantees to government and the Australian people that it is the right aeroplane," he said.

"And there has been no deviation from that thought because we have not found something that was not-perfect that has not been fixed."

F-35 a 'remarkably capable' aeroplane

Air Marshal Davies also praised the current pace of the project which Australia has been involved in for close to two decades.

"We have 450 aeroplanes flying, we're over 50,000 flight hours, we have our pilots in Arizona and our maintenance crews who fly them, maintain them, and this aeroplane is doing a really good job," he said.

"I would contend is further advanced in its maturity for this stage of its life than almost any aeroplane we've ever brought into service."

An RAAF spokesperson later clarified that there were 150 aircraft in the fleet and the two Australian F-35A aircraft had completed 450 hours of flying time.

Air Marshal Davies has praised the progress of the JSF program. ( Royal Australian Air Force )

Andrew Davies from the Australian Strategic Policy Institute said while the JSF program had been plagued with problems, he agreed the Government should persevere.

"The F-35 program has been far too ambitious for its own good and I don't think we'll ever see a program of its type again, because of the difficulties it's run into, the expenses and the time delays that have ensued," he said.

"That said, it's still likely to be a remarkably capable aeroplane."