The man responsible for enforcing Australia's international borders is pushing back against growing calls to establish a federal quarantine facility for returning travellers.
More than 25,000 Australians are stranded overseas due to the closure of international borders.
The Commonwealth has imposed a weekly cap on returning Australians to ease pressure on hotel quarantine systems run by the states.
Thousands of Australians are trying to get home but can't get on a flight.
Opposition Leader Anthony Albanese wants the prime minister to use RAAF planes to bring them home.
"There's something very practical that he can do because the RAAF VIP fleet is largely sitting idle," Mr Albanese told reporters on Tuesday.
Western Australia has joined calls for a federal quarantine facility for returning Australians after the Northern Territory said it was open to more international arrivals being housed near Darwin.
But Australian Border Force Commissioner Michael Outram said the proposal was not possible.
Early in the coronavirus pandemic, the federal government established quarantine centres on Christmas Island and at Howard Springs in the NT to house people returning from China and Japan.
Christmas Island is now being used as a detention facility.
And Mr Outram says Australian Medical Assistance Teams (AUSMAT) used to staff Howard Springs are tied up elsewhere.
He said the doctors, nurses and allied health staff were drawn from the states and territories.
"Quarantine facilities can't be run without medical professionals on the ground," Mr Outram told ABC radio.
"At the moment the AUSMAT capability, I imagine, would be pretty stretched because of the need for the states and territories to be running their own health services, plus other things going on around the pandemic."
Mr Outram said the ABF was working with the states to maximise hotel quarantine capacity, with about 12,000 beds available at any one time.
"But it's not enough if I'm being honest," he said.
"As long as the caps remain with the hotel quarantine in place it's going to be difficult to envision a situation where the airlines will start bringing more passengers."
The infrastructure department is working with international airlines to manage incoming flights.
"If that (hotel quarantine) cap was to be doubled overnight we'd be delighted, we could certainly facilitate those people through the border," Mr Outram said.
"I've got no doubt the airlines would take up the additional capacity."
Mr Outram defended his decision to allow movie star Tom Hanks and his entourage into the country when so many Australians were desperate to get home.
The ABF boss said stimulating economic activity was one factor he was obliged to take into account.
But Mr Outram insisted business travellers did not take precedence over people travelling on compassionate grounds.
People trying to leave the country must also argue their case, with 47,000 people granted travel exemptions since the border closed in March.
Tony Abbott was recently allowed to travel to London as a representative of Australia, under a category that also accommodates government ministers and defence personnel.
Mr Outram said the former prime minister was granted approval to address a parliament inquiry in the UK.
Australian Associated Press