Sydney Airport, Melbourne airport delays after major customs outage: What you need to know

Travellers have been warned to expect major delays at airports across the country due to a national software outage.

Sydney Airport said there were lengthy delays at immigration 'due to a national outage affecting Australian Border Force processing systems'.

'Passengers are being processed manually and while inbound and outbound queues are longer than usual, no flights have been impacted,' a spokesperson for the airport added.

'Passengers travelling today are encouraged to check with their airline regarding the status of their flight, and leave plenty of time when travelling to the T1 International Terminal.'

Dozens of travellers took to social media to vent their frustration.

'Sydney airport crazy right now, line has about 700 people in it waiting to get through customs,' one said.

Another said there were 'Major delays at Australian international airports as PassPort system fails'.

'I and thousands stuck at Sydney.'

Daily Mail Australia approached the Australian Border Force for comment.

This is a breaking story, more to come.