A passenger on a packed Qantas flight from Sydney to Brisbane on Monday was infectious with COVID-19.

Queensland Health warned other passengers of the diagnosis by text and then a phone

A passenger on a packed Qantas flight from Sydney to Brisbane on Monday was infectious with COVID-19.

Queensland Health warned other passengers of the diagnosis by text and then a phone call before directing them to self-quarantine in an email on Thursday.

The flight, QF520, arrived at Brisbane domestic terminal early on Monday afternoon.

A passenger on a packed Qantas flight from Sydney to Brisbane on Monday was infectious with COVID-19 (file picture)

'A person on this flight was infectious with COVID-19,' the Queensland Health email stated.

'You may be at risk of becoming unwell from exposure until midnight 27th April 2020.'

Queensland Health did not answer questions and instead referred AAP to their 'contact tracing alerts' web page.

It's unknown if the passenger knew they were infectious when they boarded the flight, or when they were diagnosed with COVID-19.

The quarantining of passengers on the Qantas flight comes as Queensland records an additional five coronavirus cases overnight, bringing the state's total of confirmed cases to 1001.

There are 21 Queenslanders in hospital, with 11 in intensive care.

Queensland Health warned other passengers of the diagnosis by text and then a phone call before directing them to self-quarantine in an email on Thursday. Passengers are pictured at Brisbane International Airport on Tuesday

Chief Health Officer Jeannette Young called the limited numbers 'excellent news', but warned of case numbers increasing while Australians are being repatriated from around the world.

Ms Young said more than 85 per cent of cases were in some way related to overseas travel.

'The numbers will get worse because of those people returning from overseas,' she said on Thursday.

'That's the group I'm concerned about.' 

On Thursday evening it was revealed that Qantas and Virgin will get federal government backing to operate key domestic routes between major cities and regional centres as coronavirus slams aviation.

The commonwealth will underwrite a range of flights, spending $165million to help the ailing airlines to stay in the air.

Deputy Prime Minister Michael McCormack said the move was about ensuring essential workers including frontline medical and defence workers were able to travel.

It will also enable the movement of crucial freight like medicine and personal protective equipment.

'We know that a strong domestic aviation network is critical to Australia's success and today's announcement demonstrates our commitment, yet again, to maintaining connectivity during this pandemic,' Mr McCormack said on Thursday night.

'This investment will also help Australians returning from overseas, who find themselves in a different city after 14 days of mandatory quarantine, complete their journey home safely.'

It covers flights from all state and territory capitals, along with Albury, Alice Springs, Coffs Harbour, Dubbo, Kalgoorlie, Mildura, Port Lincoln, Rockhampton, Tamworth, Townsville and Wagga Wagga.

The new arrangements will last for eight weeks with the government set to undertake a review which will determine if more support is needed.

The announcement is well short of the $1.4billion government bailout Virgin is hunting to stay alive.

Treasurer Josh Frydenberg is instead putting pressure on the company's shareholders.

'They've got deep pockets,' he told ABC radio on Thursday.

Mr Frydenberg said the government was continuing to talk to the company as well as Qantas, having already provided more than $1 billion in relief for the aviation industry.

'We want to see Virgin continue, we want to see two airlines in the domestic market, but we're not in the business of owning an airline,' he said.

'Where our focus has been is on providing industry-wide support.'

Prime Minister Scott Morrison said any bailouts would be sector wide, dousing Virgin's chances of a massive cash injection.

'I'm aware that there are many market-based options that are currently being pursued, and I would wish those discussions every success,' he told reporters in Canberra.

Virgin on Thursday announced a further seven-day trading halt for its shares to continue talks on financial aid and restructuring alternatives to help it weather the crisis.

But the airline didn't identify who the talks are with.

Reuters reports Virgin is also in talks with creditors about debt restructuring options such as a debt-for-equity swap and has hired UBS, Morgan Stanley, Houlihan Lokey and Deloitte as advisers.