Travellers at international airports are stuck in huge queues due to faults with electronic passport gates.
Pictures from international terminals across Australia showed huge lines both leaving and entering the country.
Emergency water bottles were handed to thousands left cramped into arrivals halls unable to enter after long-haul international flights.
The delays were caused by an IT failure of SmartGates at around 6am which Border Force and the Home Affairs department are working to fix.
It meant that all passports had to be checked manually.
Border guards were seen patrolling the enormous queues, telling travellers they may be waiting for up to two hours.
One irate passenger, David Beger, said Sydney Airport should 'be ashamed.'
He wrote: 'Sydney Airport you should be ashamed. 7am, all the international flights are landing, the epassport gates aren't working and 2,000 people are jammed into your poxy arrivals hall.'
Another, Annabelle Regan, posted a picture of crates of water bottles and added: 'Emergency supplies are coming out at Sydney Airport. Feel like we're going to be here a while.'
Another arriving passenger told Today: 'It's mayhem really. When we got in, the lines were quite long.
'But I could imagine now they would be right back to the tarmac.
We came through for our luggage - the luggage was off the carousel, sitting by the side, because that's how far it has all been banked up.'
The outage began at about 6am and was still ongoing at 8.30am.
A spokesman for the Australian Border Force said: 'The Australian Border Force is working with the Department of Home Affairs to resolve an IT systems outage impacting inbound and outbound passenger processing at international airports.
'Additional ABF staff have been deployed to process passengers and to minimise delays.
'Passengers are encouraged to arrive at airports early to allow additional time for processing.'
A Brisbane Airport spokesman said: 'The ABF smart gates were in and out and they were doing manual processing at the international terminal.
'We got staff in pretty quickly to manually process people.'
SmartGates are used at Sydney, Melbourne, Brisbane, Perth, Adelaide, Cairns, Canberra, Gold Coast and Darwin airports.