Flights returned to normal on Monday afternoon at Melbourne Airport after delays across the country due to technical problems affecting the air traffic control tower.
Airservices Australia said air traffic control operations were back to normal, with no further delays expected.
Earlier on Monday morning flights had to be halted for a period before resuming at a slowed rate as a safety precaution after the air traffic control manager detected a data fault in its digital tower system. Travellers were warned to expect delays across the country and to check with their airlines for more information.
Melbourne Airport's website showed several flights by Qantas and Virgin Australia among those that experienced delays of around 30 to 45 minutes on Monday morning. That led to flights from Sydney to other destinations around Australia experiencing delays.
In an update at 12pm, Airservices said it had found a data fault in its digital tower technology system on Monday morning.
"We have identified the defect and the system has been reset," Airservices said. "We will be closely monitoring the system throughout the afternoon to ensure it continues to operate normally."
A spokeswoman for Airservices Australia said the control tower had lost power at one point, leading to all flights being temporarily suspended.
A Qantas captain addressing passengers on a delayed flight departing Melbourne this morning described the situation as "unprecedented".
"They tried to reboot the system a number of times without success," he said.
"They've gone back to a manual system for processing aircraft."
A flight attendant said "the tower is down".
"This is the first time. It's never happened before in the 20 years I've worked here."
Fairfax's Drive editor, Toby Hagon, reported from on board a flight at Melbourne Airport that the plane's pilot said there was a queue of about 25 planes waiting to take off.
with Beau Donelly