Talks will begin in Melbourne today to try to resolve the long-running pay dispute between Qantas and three unions.

The airline and the aircraft engineers union will meet at Fair Work Australia for the first time since the impasse in which Qantas grounded its fleet.

Last Monday the industrial umpire gave the sides three weeks to reach an agreement.

The secretary of the aircraft engineers union, Steve Purvinas, says the airline's attitude today will determine if a deal can be reached in the required time.

"It's really a bit of an unknown at the moment," he said.

"If they've come in the mood to negotiate, we'll make some headway during this 21 days.

"If they want to stonewall us, as they have up until now, and they're determined to let three judges decide it after a 21-day period, well, that's another thing we'll have to cross at the time."