Virgin Australia says it has resolved a technical problem that was impacting its check-in system, as passengers report being "stuck in baggage lines for hours".
In a statement released on Monday afternoon, the airline said an IT outage was disrupting its network.
"As a result, we are experiencing congestion at a number of our check-in halls at ports and some flights have been delayed," it said.
"Our ground crew are on hand to assist guests arriving at the airport."
It later said the issue had been resolved and guests were being processed as normal for their flights.
The outage caused at least one flight to be cancelled, and photos posted online showed large queues at a number of airports.
"Passengers stuck in baggage lines for hours," ABC broadcaster Zane Bojack tweeted from Brisbane Airport.
"Can't print boarding passes or bag tags."
Similar scenes were seen in Melbourne, with passengers inundating the check-in hall.
Customer Paul Sekfy, who was booked on a cancelled flight from Melbourne to Sydney, said it had been a frustrating experience.
"Slowly but surely the look of dismay and frustration are starting to slowly dissipate," he said.
"I'm sitting here trying to work out what to do in the next couple of hours."
An IT systems outage was also blamed for long waits in processing passengers' passports at all Australian international airports last month.
The IT problem, which hit all international airports, caused the SmartGate passport control machines to go down.
