British Airways plans to keep 60% of customers flying through the first part of the planned strike by cabin crew.

The airline plans to provide flights for about 45,000 customers on March 20,21 and 22 when Unite members are due to strike, and offer thousands more seats on alternative BA flights or different carriers.

It could give no guidance on the second wave of strikes, on March 27, 28, 29 and 30, but said it would update customers after the first wave finished.

In the first strike period, BA will operate all long-haul flights to and from Gatwick and more than half of short-haul flights at the airport. All London City airport flights will operate.

Heathrow would be worst hit, as only 60% of BA  long-haul flights will operate from the airport during the first three days of action.

BA said it would operate “some” of its own shorthaul flights at Heathrow but supplement those by leasing up to 22 aircraft from eight different airlines in the UK and Europe. In total, it aimed to run 30% of its shorthaul schedule. 

It has also agreed with 40 other carriers that customers can be rebooked free of charge during the strike period if they were due to travel on a BA flight.

Chief executive Willie Walsh said the schedule was larger than originally expected because more cabin crew had offered their services than expected.

“Despite the desire of Unite’s leadership to ground the airline, the flag will continue to fly. Around 60% of our customers will be able to fly as planned and many thousands more can be rebooked onto alternative BA flights or onto rival airlines,” he said.

“I recognise the frustration of customers booked for travel from March 27 onwards, when the second stoppage is due to begin, and we will do all we can to give them more clarity about their specific flight number once we start to understand just how many cabin crew are willing to work as normal.”