ALAEA federal secretary Steve Purvinas said the union planned to re-schedule the four-hour stoppage on Friday.
"I would think that by October the 28th when the Qantas AGM takes place you're likely to see full-day stoppages," Mr Purvinas told reporters in Melbourne.
"If I was a person considering travel over the period up until Christmas I'd probably be looking at airlines other than Qantas.
"If I was a passenger I wouldn't be purchasing a ticket with them at this stage."
Qantas described the comments as outrageous and damaging, as well as counter-productive.
Wow, Steve... I thought we'd heard everything from you, but no. Please run Qantas into the ground, then you and your lemmings will have a painful, painful fall.