Australia's aerial firefighting fleet is being expanded to include planes that can respond not just to fires but to other disasters, such as floods and major storms.

It comes as longer and overlapping fire seasons are placing greater pressure on the country's existing fleet.

The recent federal budget included an extra $35 million to source more multi-use aircraft, while a national audit is underway to ensure Australia has the capacity to meet building demand.

National Emergency Management Authority (NEMA) deputy coordinator general Joe Buffone said recent fire seasons had shown the demand for more versatile aircraft.

"The key focus is to broaden the fleet so that it's multi-use," Mr Buffone said.

"This means aircraft will be able to be changed around so they can do evacuation, resupply, support remote communities and help other emergencies way beyond just fire."

NEMA is working with the states and territories and the National Aerial Firefighting Centre (NAFC) to determine the best aircraft to fill the gap.

Mr Buffone said this should also lessen the need for the Australian Defence Force to step in during disasters.

Aircraft in increasing demand

"There are some pressures on the system — we've got the northern hemisphere [fire season] that quite often overlaps with the southern hemisphere, so there's more demand on aircraft," he said.

"We're trying to make sure that we can actually have aircraft for aerial firefighting and for other emergencies, for longer periods of time as well."

Australia has about 162 aircraft contracted under the NAFC of which about 133 are Australian owned and registered.

That includes several large air tankers, 15 rotary wing helicopters that can carry up to 11,000 litres of retardant, along with a mix of smaller aircraft.

SA's fleet grows

Country Fire Service state aviation operations manager Nik Stanley said South Australia deployed its largest-ever aerial fleet last summer.

"We had 31 aircraft for this season and we have that number for the next four seasons to come," Mr Stanley said.

"We are continuously evaluating our fleet every year … looking at the capabilities that we have available, are they still suitable for us moving forward, and then also looking at what's emerging nationally and internationally with different airframe types".

SA's fleet included a helicopter dubbed the "multi-mission machine", which features a side basket capable of carrying extra equipment and a bucket for water drops.

"We just don't look at firefighting aircraft as in dropping water, but we also look at them for the other capabilities that they're able to do," he said.

"We can use that multi-machine machine in many different ways, just not fire-bombing with water."

International fire season overlap

Mr Stanley agreed competition for vital aerial resources between the northern and southern hemispheres was an increasing challenge.

"In the past, it used to be just those very large air tankers that were in North America and Europe, and then that would come down to Australia for our summer," he said.

"We're now seeing our fixed wing bomber more and more so from Australian companies going over to Europe at this time.

"So as our season extends longer, there's less time for maintenance for the contractors to get their aircraft ready to deploy over to Europe or North America.

"And then conversely, once the season finishes in the northern hemisphere, they've got to get them back so they're ready for us to commence contract when our season starts."