Unite union is set to ballot 14,000 British Airways cabin crew workers for strike action.
The airline has been in talks with Unite but has said it will still push ahead with the changes if an agreement is not reached.
Derek Simpson, general secretary of Unite, said: “BA management’s determination to impose unacceptable contractual changes on cabin crew leaves us no alternative.
“Negotiation, not imposition, is the only proper way to conduct industrial relations.”
A spokesman for British Airways previously said: “Without changes, we will continue to lose more money with every month that passes. It is essential we make ourselves more efficient if we are to ensure our long-term survival.”