Airport terminals across Australia are in chaos after the Virgin, Jetstar, Tiger and Rex computer systems crashed.
A Virgin spokeswoman said passengers were being checked-in manually by ground staff.
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She said the issue was affecting Virgin and Jetstar across Australia and the cause was not yet known.
Qantas is not affected.
Tiger passenger Warren Viti said his flight from Melbourne to Sydney was delayed for 20 minutes after they switched to manual check-in.
"They re-issued new boarding passes manually and asked the weight of our checked luggage," he said.
More to come