Four Qantas crew members who operated a flight from Chile and did not have to go into quarantine have tested positive for coronavirus, raising concerns future international flights could weaken Australia's defences against the pandemic.

All passengers on the flight from Santiago which landed in Sydney on March 29 were put in quarantine for 14 days in city hotels. But crew members were free to return to their homes under an exemption for airline crew granted by the Australian Health Protection Principal Committee, the key health crisis decision-making committee which is comprised of all state and territory chief health officers and chaired by Australia's chief medical officer.

Qantas and Virgin Australia are preparing to resume international flying to bring stranded Australians back to home.

The Age and Sydney Morning Herald can reveal four cabin crew on the flight have since tested positive for the virus. The positive test results have raised concerns inside Qantas that crew could spread the disease to family members or colleagues, according to employees who asked not to be named because they are not permitted to speak about their employer publicly.

It comes as Qantas and Virgin Australia prepare to resume international services with government subsidised flights to London, Los Angeles, Hong Kong and Auckland to bring stranded Australians home.