Seeking a settlement, the Unite union said it would not strike before this week and that "negotiation, not litigation" was the only way to avoid further walk-outs. BA is in a dispute with its cabin crew over pay as the airline tries to cut costs.
Further strikes would heap more misery on passengers travelling through London, one of the world's busiest airline hubs, after a strike earlier this year and disruptions caused by a volcanic ash cloud.
"Despite the obvious enthusiasm of colleagues here, this is not a moment for being triumphant. We shouldn't have been in this process. The case brought by BA was trivial," Unite's Derek Simpson said outside the court after the ruling.
Two out of three of Britain's top judges ruled in favour of Unite in a knife-edge decision. One of them said a small infringement in the way the strike was balloted -- the case for BA's injunction on Monday -- should not invalidate the ballot.
BA, which is in the process of merging with Spanish airline Iberia, said in a statement it was "very disappointed", adding that it had a contingency plan to keep planes in the air and fly more tha 70 percent of customers.
BA is trying to save save 62.5 million pounds ($89.7 million) a year to counter falling demand, volatile fuel prices and greater competition.
Unite said it had come to an agreement in principle with BA over its cost-cutting plans, but that the restoration of staff travel perks had not been agreed, holding up settlement of the wider dispute.
BA'S Financial Worries
Originally the union had planned to stage four strikes from May 18-22 , May 24-28 , May 30-June 3, and June 5-9.
The dispute with cabin crew over pay and conditions had already resulted in seven days of strikes in March, which cost the airline 45 million pounds.
"This increases near term uncertainty on BA's business," Davy Stockbrokers analyst Stephen Furling said of the strikes.
BA's merger with Spain's Iberia, which is eventually expected to generate 400 million euros ($497 million) a year in cost savings, will help BA recoup its strike-related losses when it it finalised later this year.
BA also expects to cut costs further by merging its transatlantic operations with American Airlines, which will allow the pair to operate as a single airline, once the tie-up is cleared by regulators.
BGC Partners analyst Howard Wheeldon said "the Iberia deal will go ahead" and many striking staff action could become "superfluous to requirements" once the merger is finalised. (Reuters)
