British Airways has been forced to cancel flights at Heathrow's Terminal 5 over the Easter period due to strike action by security workers.
The airline is expected to cancel up to 32 flights a day between Friday 31 March and Sunday 9 April (Easter Sunday).
More than 1,400 security guards who are employed by Heathrow Airports Ltd (HAL) at Terminal 5 are expected to take part in the 10-day walkout in a row over pay, the Unite union said.
A BA statement read: "Following Heathrow's requirement for us to reduce the number of passengers travelling during the period of its employees' proposed strike action, we've regrettably had to make a small number of adjustments to our schedule.
"We've apologised to customers whose travel plans have been affected and have offered them a range of options, including rebooking onto a new flight with us or another airline, or requesting a full refund.
"Our teams are continuing to work closely with Heathrow to ensure that our customers' journeys run smoothly."
A spokesperson for Heathrow Airport added: "We will not let these unnecessary strikes impact the hard-earned holidays of our passengers."
But Sharon Graham, Unite general secretary, said staff were struggling to get by and felt they had little choice but to strike.
She said: "Workers at Heathrow Airport are on poverty wages while the chief executive and senior managers enjoy huge salaries. It is the airport's workers who are fundamental to its success and they deserve a fair pay increase.
"Our members are simply unable to make ends meet due to the low wages paid by Heathrow. They are being forced to take strike action due to need not greed."
The airport said it would deploy 1,000 additional members of staff and its management team in the terminals to provide assistance to passengers over the Easter holiday.
The spokesperson said: "As at any busy time, it may take a little longer than usual to get through security, but this will be well managed and kept flowing.
"Passengers can help us ensure they get the best start to their journeys by checking their flight status with their airline before travelling to the airport, arriving at Heathrow no earlier than two hours before short haul flights and three hours before long haul flights and by being ready for security with their compliant liquids and electronics out of their hand luggage."
It comes after strike action by ground handlers at Heathrow was called off back in December after an improved pay offer was made.
Around 400 Unite union members working for Menzies, an aviation company, planned to walk out for 72 hours until a larger pay offer was put on the table.