Baggage handlers at Gatwick Airport are being balloted on strikes over pay, threatening travel disruption this summer.
Members of the GMB union at several airports, including Gatwick, Heathrow, Stansted, Birmingham and Manchester, could walk out at the end of the month if, as expected, they back action.
The ballot result is due in two weeks' time and the union would have to give one week's notice of a strike, which would coincide with the start of the school holidays, one of the busiest times for holiday flights.
The union is balloting around 1,500 workers, including baggage handlers and check-in staff.
GMB official Ed Blisset warned that a strike would have a big impact on flights.
He said: "A large number of airlines would not be able to fly because there would be no-one to load bags or check in passengers."
The union has rejected a pay offer of a 1.5 per cent increase plus a lump sum payment of £150 and is seeking a three per cent rise or a much bigger lump sum.
The dispute involves Aviance, part of the Go Ahead group, which runs ground services at airports.
Mr Blissett said: "We have been talking with the company for months but sadly we have reached the end of the road. We are not asking for an extravagant amount of money.
"Our members need decent rises to help them pay rising bills and cope with the high cost of living in places like the South East."
The union is expecting the ballot to show support for strikes.
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