A failure of the global passport control systems on Monday caused major delays for international passengers at Australian and New Zealand airports.
"Airlines experiencing difficulty checking-in travellers for international services due to outage of Advanced Passenger Processing system," the Melbourne airport operator said on its Twitter account.
The Sydney airport operator, which also issued a similar message on Twitter, said that the service has now resumed as normal.
The Australian Department of Immigration and Border Protection said in a statement it was "aware of an external system outage with the Society International Telecommunications Aeronautiques (SITA) system".
The problems were caused by crashes in the Passenger Service System program, a mandatory process in Australia for international airlines, which has forced several airlines to check-in passengers manually.
Officials believe that failures have occurred in the globally used passport control system, meaning passports could not be read electronically thus slowing down the check-in process.
In New Zealand, Auckland and Wellington airports experienced similar problems due to failures in the national system used by the country's Immigration Ministry, according to the New Zealand Herald newspaper.