Baggage handlers and check-in staff are warning that a planned strike at Luton airport over the Easter break will hit Wizz Air passengers.
Unite, the union, says around 100 of its members are due to walk out in a dispute over pay.
It claims their employer, GH London Ground Handling Services, has failed to introduce promised improvements to sick pay.
It also says GH has regularly failed to pay wages on time.
Unite Regional Officer Jeff Hodges said: “GH London has a rapidly closing window of time to stop Easter holiday disruption for Wizz Air passengers.
“The company seems to have gone out of its way to treat employees with contempt but there is still time for these strikes to be avoided. GH London simply has to keep its promises on sick pay and fix its payroll system.”
The strikes are due to take place between 14 April and 19 April.