British Airways staff at Heathrow are to ballot on industrial action, which could disrupt the busy summer period.
Unions Unite and GMB said the dates for the ballot, to be held among check-in and ground staff, will be confirmed during the next few days.
The unions say their members have not had a 10% pay cut imposed during the pandemic reinstated.
GMB National Officer Nadine Houghton said: “If BA wants to avoid industrial action that will trash many people’s summer holidays, they need to do what’s right by check in staff.”
Unite General Secretary Sharon Graham said: “BA has had every opportunity to resolve this dispute through negotiations but it has failed to do so. Our members are left with no choice but to vote for strike action this summer.
“Unite will be giving its members its unequivocal support until this dispute is resolved.”