British Airways is cancelling approximately 32 flights a day to and from Heathrow Airport at the start of the Easter holidays.
The move is due to a planned 10-day strike by 1 thousand 400 security workers in the Unite union who are taking action in a dispute over pay.
British Airways said it had offered a range of options to affected customers.
Heathrow says contingency plans will be put in place to ensure it can operate as normal.
The walkout is due to start this Friday and end April 9.
The airline has been told by the airport to reduce its schedule on those days by 5 per cent and has stopped selling tickets.
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