British Airways has been forced to cancel all passenger flights out of Heathrow for two days next week because of a strike by thousands of cabin crew.
Domestic and European flights to and from Gatwick will also be grounded on the two days - Tuesday and Wednesday - following the breakdown of talks aimed at resolving a bitter row over sickness absence, pay and staffing.
Hundreds of thousands of passengers will be hit by the news, which will lead to hundreds of flights being cancelled.
BA chief executive Willie Walsh said: "We are deeply sorry that our customers are the innocent victims of this unnecessary and unjustified strike."
The airline said it was still trying to reach a deal with the Transport and General Workers Union before the start of the strike next Tuesday but wanted to give customers early warning of its schedule to give them time to make alternative arrangements.
The union has called two further three-day walkouts from February 5 and February 12 unless the deadlock is broken.
Mr Walsh said: "More than 15,000 customers a day have contacted us since the union announced a series of 72-hour strikes, extremely concerned about their winter holidays and business trips.
"Announcing our contingency plans means we can end uncertainty for customers caught up in the first round of strikes and help them make other plans.
"If we postponed the cancellation of flights until the eve of a strike, customers would have virtually no time to make alternative arrangements.
"We remain absolutely determined to search for a negotiated settlement and our door remains open to the T&G, day or night. We regret that the T&G has not supported our initiative to seek the assistance of the Acas conciliation service."
