Virgin Australia and Jetstar flights from Sydney to Perth have been grounded amid chaos caused by a power outage at Sydney Airport's Terminal 2.
Major disruptions are expected network wide if the issue is not resolved quickly.
Airlines that operate from the T2 terminal include JetStar, Virgin and Tiger airlines.
Planes are reportedly being redirected away from the airport, with incoming flights delayed.
Virgin Australia has four flights a day between Sydney and Perth.
Virgin Australia is advising customers to avoiding travelling to Sydney Airport.
Sydney Airport is trying to resolve this issue however in the meantime Virgin Australia is unable to check-in or board flights at Sydney Airport T2.
An airline spokesperson said that “this is causing extensive delays to our services and will result in cancellations today.”
“At this stage we advise guests travelling to or from Sydney Airport Domestic T2 to refrain from turning up at the airport.”
“We will provide another update on this page at 11.30am.”
The airline has assured passengers that if they are due to travel to or from Sydney airport today and choose not to fly, they will get a refund or free of charge flight change within 7 days.
It added that it is experiencing high call volumes and strongly recommends waiting to call until tomorrow to call regarding flights.
Jetstar has cancelled numerous flights network wide.