More than 1,700 British Airways flights have been cancelled as pilots begin a two-day strike in a row over pay.
It is the first time BA pilots have staged a strike, which began at midnight.
BA has offered pilots a pay rise of 11.5 per cent over three years, but the British Airline Pilots Association (Balpa) says its members wanted a bigger share of the company's profits.
The airline said 195,000 customers will be affected by the walkouts.
Chief executive of BA, Alex Cruz, apologised: “I'm really sorry for the position the cynical actions the pilots' union has put us in. It's by all accounts an own-goal for the union.”
But Balpa general secretary Brian Strutton said BA bosses need to “wake up” and accused them “putting profits before the needs of passengers and staff”.
He said: “British Airways must now put the needs of its staff and passengers first and accept that its pilots will not be bullied or fobbed off.”
Both sides have said they want to resume talks, but there is little or no sign of the deadlock being broken.
Since the strike dates were announced in August, BA received 111,000 tweets and 394,000 calls from concerned customers, and had to triple the number of staff supporting customer contact teams.
Passengers have been offered refunds or the option to rebook an alternative travel date or time.
Heathrow airport is set to be the worst affected as BA’s busiest hub.
It has been described as a "ghost town" by visitors to the airport today, with Twitter user Rahul Kalia sharing a photo of the airport's Terminal 5, which shows it completely empty.
Meanwhile, BA Cityflyer flights will not be affected by the dispute.