Ryanair pledged to push ahead with flights to and from Stansted airport this weekend even if baggage handlers and check-in staff carry out threats to go on strike.
Talks continued last night to try to prevent a two-day walkout at the busy holiday airport.
The row involves the Transport and general Workers Union (TGWU) and GMB unions and Swissport, the ground-handling agent for airlines at the London airport.
For the second day running, the meeting of the two sides was being hosted by conciliation service Acas. It was thought that the sides were still far apart and that there was little likelihood of a breakthrough.
Ryanair said it had written to passengers due to travel during the proposed strike and advised them they could use the carrier's online check-in facility instead. They may, however, have to travel without any checked luggage.
More than 500 GMB union members employed by Swissport have voted to strike from 5am on Saturday until 8am the following day, and again on Monday, a UK bank holiday, from 5am until 8am on Tuesday.
Flights at the airport will be "severely disrupted" by the walkouts, GMB predicted.
The threat comes just as British airports are returning to a more normal routine after the disruption caused by the recent terror alerts.
Swissport holds the ground-handling contracts for Ryanair and EasyJet, as well as a number of charter airlines.
The workers provide ground-handling services, including check-in and baggage handling, for about 80 per cent of the passengers who use the London airport.
"Ryanair believes that the GMB and Swissport should sort out their differences without trying to blackmail the travelling public," the airline said in a statement. "However, any strike, if it proceeds, will not be allowed to disrupt Ryanair's flights at Stansted next weekend."
GMB said it submitted a pay claim in April, including calls for a premium rate for working on Sundays as well as a "substantial" pay review.
Swissport has not met the claim for Sunday premiums, according to the union, and the pay offer it has put on the table had "unacceptable" strings attached.
Ryanair said yesterday that Swissport workers earn double time for working on bank holiday weekends and that "the travelling public should not be held to ransom by the GMB" during such a busy time.
- (Additional reporting PA)
