The US general heading up the controversial F-35 program says there's not an aircraft in the world that could take the fighter plane on and survive.

Responding to critics who claim the F-35 will be shot out of the sky by new Russian aircraft, Lieutenant General Chris Bogdan, said they didn't have the data he had.

General Bogdan, who will appear before a Senate inquiry into the F-35 on Thursday, also predicted costs - now around US$85 million per aircraft - could fall by up to 10 per cent under a proposed acquisition to maximise production savings.

Australia plans to buy 72 F-35 aircraft and perhaps as many as 100.

Australia's first two aircraft are now part of the flight training pool in the US. The first arrives in Australia in 2018, with three RAAF squadrons equipped with F-35 and to operational by 2023.

The F-35 program has been controversial, with cost blowouts and technical problems. Some challenges remain, especially in fully developing complex mission software.

A number of critics claims F-35 will be shot from the sky by new advanced Russian aircraft now entering service across the region.

General Bogdan said the critics didn't have the data he had.

"I have the pilots who are flying the airplane. You can go ask them. There is not an airplane in the world today anywhere that if put up against an F-35 in an air-to-air environment that we would not see them first, shoot them first and kill them first," he told reporters.

F-35 aircraft have been manufactured in production lots, according to customer funding commitments. It's been proposed that production lots 12, 13 and 14 - more than 500 aircraft including some for Australia - be combined.

That would allow industry to purchase components in quantity.

"If we do that the total savings to the 14 customers could be in excess of $US2 billion ($A2.77 billion). That is a lot of money to save if you are going to buy airplanes anyway," he said.

General Bogdan said the program office calculated that could result in savings of five to 10 per cent per aircraft.

On current estimates Australia will pay $US85 million ($A117.76 million) per aircraft in 2019 and savings from a block buy could take that below $US80 million ($A110.83 million).

Later on Wednesday, General Bogdan's planned private briefing of the Senate committee inquiring into the F-35 was cancelled because of a clash with the launch of the defence white paper.

Greens defence spokesman Senator Peter Whish-Wilson, who instigated this inquiry, said he was disappointed the briefing, at least a month in the planning, had been cancelled at the last minute.

"I will continue to push that Lieutenant General Chris Bogdan is given an opportunity to be questioned over the Joint Strike Fighter in public," he said in a statement.