"Sydney airport security screening isn't working this morning, so every passenger for the next 2 hours' worth of domestic flights is now crushed into the check in area waiting for the gates to open", tweeted one.
A security incident is causing significant delays at Brisbane Airport's worldwide terminal.
Virgin Australia flights were also recovering from significant delays, which included two cancellations.
Virgin Australia said that "due to a technical issue" passengers were being processed at reduced capacity. Photos and videos of the airport showed uncomfortably long queues as passengers crowded the terminal as a result of the outage.
The other domestic terminal, T3, is operated by Qantas and is not experiencing an issue.More news: Amazon could expand Alexa's smart home offerings post Ring acquisition
"We're working to resolve the issue as quickly as possible and thank you for your patience".
At around 7:45AM Sydney Airport Tweeted that it was once again processing passengers in the affected terminals.
"The safety and security of our passengers is our number one priority and we are pleased to say that all systems are operating as normal", an airport spokesman said in a statement.
Outbound flights, but not inbound flights, were experiencing delays.
The glitch affected systems including the CCTV video surveillance prior to the opening of Terminal 1 and 2, an airport spokesperson told Xinhua.