The union representing British Airways cabin crew, Unite, has threatened more strikes after Easter unless there is a breakthrough in talks.
Ninety flights were cancelled yesterday as cabin crew began a four-day strike, due to run until Tuesday.
It is the second walkout by cabin crew in a dispute over pay and conditions.
British Airways says it expects to fly more than 75% of its customers, around 180,000 of the 240,000 people who had planned to travel in the period covered by the strike.
A BA spokesman said: ‘At Heathrow we are flying our increased schedule and dozens of flights have departed, many very full with customers looking forward to their Easter holidays.
‘The numbers of cabin crew reporting at Heathrow are currently at the levels we need to operate our published schedule.
‘Our operations at Gatwick, where we aim to fly our entire normal schedule, continue to be exceptional with a large number of flights departing early.
‘Cabin crew are continuing to report as normal at Gatwick, just as they did last weekend during the first strike period.’
Len McCluskey, Unite assistant general secretary, said: ‘This is the great BA con trick. It's a three-card trick Paul Daniels would be proud of.
‘BA is claiming that it can function but it is doing so by throwing away millions of pounds every day as it dumps its passengers on other carriers.
'Passengers who turn up expecting to fly BA, a brand they trust and have paid a premium for, will now be shipped on to carriers they've never heard of.'
Passengers between Ireland and Britain are still unaffected but could be hit if they have booked onward travel from Heathrow.
