Holidaymakers looking to jet off for half-term next month face airport chaos, with hundreds of Heathrow staff threatening to strike.
Fed up ground staff and baggage handlers - employed by Menzies Aviation - could walk off the job for three days from February 11, in a dispute over pay.
It comes as new Covid rules arrive next week - making it easier for Brits to travel.
The EU has given the green light for travellers who have recovered from the virus within 180 days or had a second vaccine dose with 270 days will be able to enter Europe without doing a test.
While kids who caught Covid with just one jab can also enter more freely.
Menzies provides ground and cargo handling and forwarding, as well as into-plane fuelling staff for the likes of Qantas, American Airlines and British Airways at the London-based airport.
Extensive security protocols to combat terrorism will make the employees difficult to temporarily replace at such short notice.
Many of the reported 400 staff involved belong to the Unite union.
Unite is urging retrospective pay rises for 2020 and 2021, citing Swissport and Cobalt as examples of rivals who agreed similar pay deals with their workers.
It said impacted Menzies workers are "being treated as second class citizens", while those in the cargo division secured a seven percent pay rise last year.
In a statement on its website, Unite general secretary Sharon Graham said: "The UK is facing a cost of living crisis and our members at Menzies realise that a two-year pay freeze will make it impossible to make ends meet.
"Unite fights to defend the jobs, pay and conditions of our members. We make no apology for demanding that Menzies makes a fair pay offer to its workers.
"Unite will be defending our members’ interests to the hilt until this dispute is resolved."
The strike ballot closed on Thursday (January 27).
Unite regional officer Kevin Hall added: "If strike action goes ahead it will cause disruption and cancellations throughout Heathrow, potentially impacting on half term trips and skiing holidays.
"Industrial action can still be prevented if Menzies takes a leaf out of its competitors' handbooks, enters into meaningful negotiations with Unite and makes a fair pay offer."
Ms Graham also told the Daily Mail, the firm "cynically used the cover of the pandemic to fire and rehire its workers to boost long-term profits".
Phil Lloyd, Senior Vice President UK at Menzies Aviation, said: "We are very disappointed that Unite are choosing to pursue this course of action at a time when everyone in the industry is attempting to rebuild consumer confidence and safeguard employment by restoring flight schedules."
Mr Lloyd said he understood only 146 of around 1,700 workers voted for the strike action and the firm is "very confident" it will not cause disruption.
He added: "We are very empathetic to the cost of living increases our entire team are experiencing and have been having meaningful discussions with the GMB on the issue and we would like to have the same open and transparent discussions with Unite as we have done at many other UK airports where we operate."
A meeting between Menzies and Unite is set to take place on Monday.
A Heathrow spokesperson told the Mirror: "We are aware of an industrial action ballot for Menzies employees who support airlines operating out of Heathrow.
"It would not be appropriate for us to comment on the ongoing discussions they are having with their employer.
"As always, we remain in constant dialogue with all partners who operate at Heathrow and will continue to do everything we can to ensure passengers can enjoy a safe and reliable journey."
We have also contacted Menzies for further comment.
