British Airways cabin crew could be going on strike.
Members of Unite are to be polled on whether to take industrial action in a dispute over pay, with voting starting next week. The result is due in mid-December.
The union said crew had rejected a 2% pay offer.
Regional officer Matt Smith said: "British Airways, once the 'world's favourite airline' is fast becoming the 'world's least liked', paying poverty wages while its parent company predicts annual earnings of £4.7 billion between this year and 2020.
"It should be to the company's eternal shame that they, the UK's national carrier, are making billions while their cabin crew, responsible for maintaining a safe environment, are working while sick and without adequate rest."
The dispute involves around 2,000 Unite members based at Heathrow Airport who joined BA from 2010 as so-called Mixed Fleet.
The union claimed crew were having to sleep in their cars in between shifts because they could not afford to drive home, adding that basic pay started at £16,000.
Unite said some workers were doing other jobs on their days off to make ends meet.
A BA spokesman said: "Our pay proposal for our Mixed Fleet cabin crew is fair, reasonable and consistent with that already accepted by other British Airways colleagues.
"It reflects typical pay awards given by other companies in the UK and will ensure their reward levels remain in line with cabin crew at our airline competitors.
"We remain open and flexible to discuss this further with our colleagues and the union."