Sydney Airport has begun processing passengers after it came to a standstill on Friday morning following "technical issues" that affected two of its terminals.
Outbound passengers at Sydney's T1 International and T2 Domestic terminals were prevented from checking in for their scheduled flights, and airline staff were reportedly processing some passengers manually.
"We're experiencing technical issues at T1 and T2 causing interruptions to passenger processing and delays," the airport posted on Twitter. "We're working to resolve the issue as quickly as possible and thank you for your patience.
"We're advising passengers and visitors to avoid T1 and T2 until further notice."
Qantas was not impacted by the technical issues, with the airport's T3 terminal operating as per normal.
In a tweet, Virgin Australia said at 8.40am AEDT Friday, security screening at the airport had reopened and it was operating at normal capacity.
"Security screening at Sydney Airport is now operating at normal capacity following an earlier technical issue. As a result, some Virgin Australia services may be impacted," the airline wrote.
Sydney Airport also took to Twitter to report it was catching up on its backlog of delayed passengers.
"We are now processing passengers at Sydney Airport. We are working hard to catch up any delays," the airport said.
Passengers travelling to or from Sydney Airport in September were met with a two hour-plus delay due to an Airservices system suffering an IT issue.