The royal commission, which is examining issues of jurisdictional coordination in the wake of the 2019-20 bushfires, was told the closest aircraft often could not respond to a fire if there was a border involved.

Ruth Ryan - the corporate fire manager HVP Plantations - said she would like to see state borders "effectively dissolved" if there was a fire approaching.

HVP Plantations manages 240,000 hectares of land across Victoria, including in the south-west of the estate.

While there are two firefighting aircraft based at Mt Gambier, about 10 kilometres into South Australia, they are only allowed to respond to fires up to 25 kilometres over the border.

"Once you get beyond that 25 kilometre area, then it's got to go through the state air desks in both states and that adds time to the take-off," Ms Ryan said.

"I would certainly like to see the state borders dissolved effectively for aerial support, so that the closest aircraft respond to every fire and as you don't have those 25 kilometre natural borders."

Ms Ryan also said there needed to be common training and equipment between states.

"You know, if I was sitting 20 kilometres inside the Victorian border, I cannot, unless I've got yet another radio in my vehicle, I cannot hear what's happening in South Australia as far as any despatch," Ms Ryan said.

National Aerial Firefighting Centre general manager Richard Alder said aircraft that work across jurisdictions often need to be fitted with two different radio units.

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That could hamper efforts to share aircraft with different states.

"Each state and territory adopts a different system that are largely incompatible," Mr Alder said.

The commission will hear on Wednesday from the Australian Defence Force Vice Admiral David Johnson and Lieutenant General Greg Bilton about the military's role in responding to the summer's bushfires.