Ground handlers employed by a private contractor at Heathrow Airport are to strike in a row over pay.
Around 350 members of Unite working for Menzies will walk out for 72 hours from 4am on Friday December 16.
The action will lead to some flight disruption, the union said.
General secretary Sharon Graham said: “Menzies needs to have a long, hard look at itself.
“This is a highly lucrative company, which has made a fair pay offer to one group of its workers but isn’t prepared to make a similar offer to its ground handlers.
“Unite is entirely dedicated to defending its members’ jobs, pay and conditions.
“Our members at Menzies will continue to receive the union’s complete support.”
Unite said the ground handlers have been offered a flat rate increase – which it branded a real-terms pay cut.
A Heathrow spokesman said: “We are aware of industrial action proposed by Menzies colleagues from 16-18 December.
“We encourage airport partners who would be affected to continue with their contingency planning and we will support them to minimise the impact on passengers, should the strike go ahead.”