Qantas is being accused of "taking advantage" of the pandemic to "blow up" workplace agreements with international flight attendants.

The Australian airline went to the Fair Work Commission this week to terminate its enterprise deal with long-haul cabin crew.

The application to the Fair Work Commission comes as the cabin crew, their union and Qantas have been in stalled negotiations over changing the terms of the workers' agreement.

This is the first time in its history that Qantas has tried to tear up an existing workplace agreement.

University of Adelaide workplace law expert Andrew Stewart said the airline was "taking the nuclear option".

"It's the nuclear option in the sense that it's taking years and years of negotiated arrangements and just blowing them up — or at least signalling a willingness to blow them up in order to achieve a very, very different set of conditions for the affected staff," Professor Stewart said.

What is the sticking point in negotiations?

Qantas said in a statement it wanted to adjust its Long Haul Cabin Crew Agreement "to change restrictive and outdated rostering processes".

It said the current arrangements meant that about 20 per cent of its 2,500 long-haul crew could only be used on a single type of aircraft.

Under the existing agreement, cabin crew on the A330 fleet cannot be used on the 787 and A380 fleets, making it more difficult for Qantas to shift aircraft types.

"Which is unworkable as the airline seeks to recover from COVID," it said.

Qantas said it offered the workers more money and allowances in return for changing those arrangements, but both the workers' union, the Flight Attendant's Association of Australia (FAAA), and 97 per cent of staff who voted turned down the offer.

"Asking to terminate the current agreement is the last thing we want, but we're stuck between a rock and a hard place," Qantas International's chief executive, Andrew David, said in a statement.

"The FAAA ran a scare campaign against the new deal, claiming it would mean redundancies and offshoring, despite the fact that we're currently hiring new crew in Australia.

"The union's default position is that the company can't be trusted and should always give more. That's simply wrong."

'Breaking the backs' of staff it called 'heroes'

FAAA federal secretary Teri O'Toole told the ABC the airline's comments about its negotiation tactics were "completely untrue".

"We didn't run a scare campaign at all. It's simply untrue," she responded.

"The equivalent is if you go to work for four weeks and one of those weeks you have no idea where you'll be. You can't plan your life.

"Cabin crew are no longer single people. They aren't so inflexible that they can have this insecurity."

Ms O'Toole said the union agreed with Qantas on most of the changes it offered and even came to it with a halfway agreement on the roster flexibility changes.

"They're making out that we've said no to everything," she said.

"We've given them so much of what they wanted. We want to negotiate.

Ms O'Toole said the morale among the staff was "shocking" and many of them had just put themselves at risk by working on international repatriations flights to get Australians home during the pandemic.

"These staff were heroes last week who went into COVID-infected hotspots to rescue Australians even before vaccinations. They've been in quarantine in Howard Springs [in Darwin]," she said.

"Now they're heroes but they're not worth anything and we'll break their backs.

"It's wrong. It's not the spirit."

The Australian Council of Trade Unions (ACTU) has also come out against Qantas' lodgement in the Fair Work Commission.

It noted that if the Qantas application was successful, some of the flight attendants could be reverted to an industry award that offered far less money than the current agreement.

It said this would see some wages cut by half.

"Qantas has received billions in taxpayer funds over the last two years," ACTU president Michele O'Neil said.

'Obvious tactic' won't make unions back down

The University of Adelaide's Professor Stewart said, at this stage, the move by Qantas was largely a threat.

"The threat of following through and getting termination of the agreement would put very significant pressure on the cabin crew and their union to reconsider their bargaining stance," he said.

"I think it's highly unlikely that it's going to cause [the union] to fold on the some of the key issues."

Professor Stewart says what was interesting about Qantas' move was that it signalled how the airline wanted to operate in the future.

"There's a much bigger context, and a much bigger contest going on here, which is really about what kind of business Qantas is going to be in the future," he said.

"It's a clear attack on an existing part of their conditions.

"It's sending a signal, which Qantas sent in other parts of this business over the last few years as well, that it sees its future profitability being tied to slashing its labour costs and maintaining its profitability.

"But in the short term, this is just an obvious bargaining tactic that was open to Qantas."