As part of a pay dispute, unions have called for EasyJet cabin crew based in Spain to strike for nine days in July.
The strike would exacerbate passenger concerns as airlines struggle to meet demand after Covid restrictions were lifted.
Because of staff shortages at Gatwick, EasyJet has already had to cancel thousands of flights this summer.
Meanwhile, Heathrow Airport is still cleaning up after 5,000 flight cancellations on Monday.
EasyJet and the Spanish union USO have been negotiating cabin crew pay since February, but have reached a “deadlock situation,” according to the union.
It has called a series of 24-hour strikes throughout July which could affect British holidaymakers.
Flight attendants want a 40% raise in basic pay, according to Miguel Galan, USO general secretary for EasyJet Malaga.
He claimed that the pay of Spanish cabin crew is not comparable to that of their French or German counterparts.
According to the union, the basic pay for EasyJet’s Spanish crew is €950 per month (£816), excluding bonuses and extra pay.
According to the BBC, basic pay accounts for 60 percent of EasyJet employees’ salaries, with the remaining 40 percent determined by factors such as how many flights the crew works.
Mr Galan said the USO union, which claims to represent 80 percent of the 450 EasyJet employees in Spain, is still hopeful that an agreement can be reached to avoid the strikes during a meeting with management on Tuesday.