More than 1,000 Qantas domestic flight attendants have voted in favour of strike action after being asked to work longer shifts and have shorter break times.
The Flight Attendants' Association of Australia (FAAA) said 99 per cent of votes received were in favour of industrial action.
The FAAA's action could include strikes for up to 24 hours, sparking possible threats to domestic flights over the Christmas holidays.
Qantas’ enterprise agreement offer would extend domestic cabin crew shifts from 9.5 hours to 12 hours, and up to 14 hours if there is a disruption.
The proposed agreement reduces rest periods to 10 hours, which the union said could increase fatigue issues.
The airline has also offered its unionised workers 3 per cent annual pay rises for four years.
This follows a two-year pay freeze that was enforced when Qantas planes were grounded due to COVID-19.
No date for strikes or deadline for a return offer from Qantas has been announced.
FAAA aims to 'minimise disruption' over holidays
The FAAA has reassured Australians that it "aims to take a measured approach to any industrial action that minimises disruption to the travelling public, especially over the upcoming Christmas holiday peak".
"We are seeking a fair offer that doesn't send flight attendant pay and conditions backwards," the union said in a statement.
Qantas has around 1,500 short-haul cabin crew and the union would need to give three business days of notice before taking any action.
This could also include overtime bans and refraining from boarding responsibilities, according to paperwork filed with the Fair Work Commission.
Qantas describes vote as 'very disappointing'
"This is a very disappointing step by FAAA given we're continuing to negotiate towards a new agreement," a Qantas spokesperson said.
On Wednesday, the airline lifted its first-half profit forecast for the second time in six weeks on strong travel demand, claiming its debt was reducing faster than expected, allowing it to consider further returns to shareholders in February.
Qantas said consumers were still putting a high priority on travel ahead of other spending.
It said there were signs that limits on international capacity and higher prices for overseas travel was driving more domestic leisure demand, benefiting Australian tourism.
Travel plans disrupted by the pandemic have left hundreds of thousands of Australians with billions of dollars of flight credits, but there have been issues around flight credit schemes, including incomprehensible terms and conditions and the inability to transfer them to family members.
The airline said that around 60 per cent of the $2 billion in COVID-related travel credits had now been redeemed by customers.
ABC with Reuters