The passenger processing system used at Australia's international airports is back up and running after causing lengthy delays in terminals including Brisbane, Melbourne, Sydney, and Auckland.
International passengers were being checked-in manually as a result of the outage, causing long queues and delayed flights.
The Society International Telecommunications Aeronautiques (SITA)-owned Advanced Passenger Processing (APP) system was down until shortly after 10am AEST, though delays in passport processing continued as airlines worked to clear the backlog of passengers.
By 11:10am AEST, Melbourne Airport advised on Twitter that the APP system was running as usual.
The Australian Border Force announced that it had deployed extra officers at airports to minimise the impact of the outage on passengers.
A spokesperson from SITA told ZDNet via email that the cause of the incident was a network connectivity issue, not a cyber attack.
"This was caused by a major telecom failure in the UK of a top provider to our datacenter. In response, we implemented an alternative communications link and resumed services," the spokesperson said.
"Though the service is currently restored, our team remains on high alert."
According to the Department of Immigration and Border Protection, all international flights to and from Australia are subject to mandatory APP reporting provided by airlines through the APP system.
The system has been a key component of Australia's border management strategy for decades and incorporates passenger pre-clearance prior to boarding an aircraft and faster immigration and customs passenger processing.
"This facilitates a more streamlined border clearance process for travellers and enhances the Australian government's ability to target security concerns," it states on the department's website.
At the start of the year, the Immigration department announced it was looking to deploy self-processing systems that use fingerprints, iris, or facial structure recognition to check in passengers at major airports and seaports in Australia.
Immigration Minister Peter Dutton told the ABC in January that the aim of the AU$78 million upgrade is to cut down manual processing and paperwork by more than 90 percent, boost tourism, and increase national security by making it easier to detect threats.
Updated 9.00 am AEST 23 May 2017: Added comments from SITA.