Jetstar employees are facing at least a day with no pay due to a glitch at ANZ.
The bank has taken responsibility for the problem, according to reports.
"Jetstar employees are often living paycheque to paycheque, so a problem like this can cause major issues," says an aviation union spokesman.
Kelvin Ellis of the Et Tu union said many Jetstar staff will be overseas, in the air or otherwise uncontactable today.
"They can't easily rearrange their bill payments and other finances at the drop of a hat just because the bank made a mistake."
The union is working with Jetstar to resolve the issue as soon as possible, Mr Ellis says.
ANZ expects the glitch to be resolved by the end of the day.