Nearly 400,000 people abandoned British Airways in May as strikes by cabin crew forced the airline to cancel hundreds of flights.

The flag carrier said that passenger numbers fell by 14.2 per cent to 2.3 million last month following a wave of industrial action that disrupted services in the last two weeks of May.

BA’s revenue per passenger numbers last month fell by 11.5 per cent as a result of the strike. The fall was steepest in economy class, which was down 12.5 per cent, while the premium cabins were down 6.5 per cent.

Meanwhile rivals including easyJet and Virgin have been experiencing a rush of bookings as passengers shun BA.

Despite the impact of the ash cloud, easyJet flew 7.9 percent more people in May than a year ago. The average load factor rose to 85.8 percent, compared with 83.5 percent in May 2009, and a total of 4.25 million people took a flight with Easyjet in May, up from 3.95 million last year.

Ryanair said that its passenger numbers increased by 12.3 per cent to 6.19 million last month. Its load factor was unchanged at 81 per cent.

Richard Branson has said that Virgin Atlantic, which this week flew the England football team to South Africa, is currently experiencing a surge in forward bookings due to the BA strike. Its load factors are over 90 percent in May, compared to BA’s falling 5.4 percent to 69.7 per cent.

The last walk out by BA cabin crew ended last night, however the third and final strike of the series of three begins on Saturday.

Talks between BA management and workers’ union Unite have stalled yet again this week over failure to agree on reinstating travel perks. Unite is now threatening to hold a fresh ballot to vote for strike action over the summer holidays.

BA says it operated 70 per cent of its services during the most recent strike period and it expects 80 per cent of flights to operate from Saturday as cabin crew begin to return to work.

However the strikes have cost BA £120 million to date and the airline is facing further losses of £7 million for every additional day of industrial action. Unite has estimated that the long-term damage to BA’s reputation could cost the airline about £1.4 billion.

BA said: “The total cost of the strike period can only be assessed at the end of the disruption and will reflect lost bookings and reduced travel volumes offset by some volume driven cost savings.”

Willie Walsh, the airline’s chief executive, has promised to increase the number of flights operated during any future industrial action and believes that it will be possible to offer a full service even if cabin crew are on strike.