Families reunited in emotional scenes at Sydney's international airport on Monday, as Australia's border reopened almost 600 days after a pandemic closure began.

Australia has finally lifted its ban on citizens travelling overseas without permission, while the two largest cities, Sydney and Melbourne, now allow vaccinated Australians to arrive without quarantine of any kind.

On March 20 last year, Australia introduced some of the world's toughest border restrictions in response to the coronavirus pandemic, halting almost all travel to the island continent. Critics had dubbed the country a "hermit state".

Families have been split across continents, and tens of thousands of nationals were stranded overseas, with those gaining permission to enter forced to spend thousands of dollars and agree to spend 14 days locked in a hotel room.

Tim Turner, who hadn't seen his son for more than a year, said it was "pretty brilliant" that they were now able to reunite.

Touching down in Sydney was "beautiful, beautiful", he told reporters at the airport.

Australian airline Qantas had grounded much of its fleet for more than 18 months, with CEO Alan Joyce calling the resumption of regular international flights "a long time coming".

"It's wonderful to see Australians able to reunite with loved ones after such a long time apart," he said.

Prime Minister Scott Morrison said it was a "big day for Australia", posting on Facebook that the country was now "ready for take-off!"

Travel is expected to resume slowly after such a protracted shutdown, with low passenger numbers on the first flights to arrive.

More than one million foreign residents remain stuck in Australia unable to see friends or relatives overseas, with the relaxed travel rules applying mainly to citizens.

And some Australian states with lower vaccination rates will remain virtually closed to the world, as they still have mandatory and costly 14-day hotel quarantine requirements in place.