Heathrow Airport will cancel 1[ads1]77 flights Monday and Tuesday after a union vote rejected a wage offer.
Around 4,000 Unite members including engineers, firefighters and security staff voted for the airport's revised agreement, with 88% opting to strike.
If walk-outs continue, Unite says, nearly 2,500 employees will miss work.
Heathrow is not yet announcing which flights will be canceled, and said passengers should check with their airlines to see if they were affected. .
Affected passengers may be offered other flights or reimbursement by their airline, it added.
Heathrow said the flight cancellation, which affects 91 airlines including British Airways, was a preventive measure in case a solution was not found.
Conversations between union leaders and Heathrow leadership at the Acas Conciliation Council, aimed at averting the strike action, lasted until late Friday and resumed on Saturday.
The airport, which advised passengers to check the website for updates, said that emergency plans would keep Heathrow open and safe on both strike days, albeit with some disruption.
Passengers who still plan to fly on Monday and Tuesday have been warned to arrive at least three hours ahead of long-haul flights and two hours ahead of short-haul flights, as it may take longer to get through security.
& # 39; Growing anger & # 39;
A Heathrow spokeswoman said: "I can confirm that we are working with our flight partners to consolidate and reduce the number of flights operating during the strike period.
" We have proactively canceled 177 flights departing from Heathrow over Monday and Tuesday.
"Passengers on these flights will either have been rebooked for alternative services or given a refund."
Uniting regional coordination officer Wayne King said: "This latest strike action indicates growing anger among airport workers in a number of important jobs that are essential for the smooth and safe operation of Heathrow.
" Airport managers need to follow this the latest strike sentiment and the overwhelming refusal of our members of the revised pay offer that adds little to the initial pay of £ 3.75 extra a day for many workers. "
Meanwhile, talks have focused on averting a strike by British Airways pilots are set to continue next week.
British Airline Pilots Association (Balpa) executives met last week to try to resolve the pay dispute.
The union had to give two weeks' notice of industrial action.
claim compensation if my flight is canceled?
If your flight out of Heathrow is canceled, you should contact your airline to see what you are entitled to in terms of reimbursement or compensation.
If your flight was canceled due to strikes at the airport (rather than the airline), you are unlikely to be able to claim compensation as this would be considered "extraordinary circumstances" beyond the airline's control, Civil Aviation That's what the authority said.
The CAA added that the airport is not obliged to pay compensation directly to passengers, and whether the airport provides its customers (airlines) with compensation is a commercial matter between the two parties.
If your flight has been canceled because airlines strike, said the CAA, then this would be considered under the airline's control, and therefore you have a legal right to either:
- A full refund, and this includes flights on the same the journey that may be from another airline (for example, a flight back or forth)
- A replacement flight to get to your destination
- Or, if you are a full way through your journey and do not want a replacement flight ght, you are entitled to a return flight to the airport you originally departed from
If the cancellation delays you by two hours or more, you are also legally entitled to compensation and assistance at all costs you may incur as a result of delay.
Are you going to fly on Monday or Tuesday? Has your aircraft been affected? Please contact by emailing
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