British Airways has won a High Court injunction to stop the latest strikes by its cabin staff.
The decision was based on a technicality and whether the Unite union followed rules in contacting its members with strike result details.
The first of four five-day walkouts had been due to begin at midnight, but will not go ahead following Mr Justice McCombe's decision.
The union said it would appeal against the injunction decision.
BA said it was delighted that the "extreme and unjustified" strike could not go ahead.
But it apologised to some customers who are due to travel during the early days of the union's planned industrial action and will see flights affected.
It had already announced a rearranged Heathrow schedule to give customers as much notice as possible about changes to their travel plans necessitated by the strike call, it said.
"Ash disruption permitting, we will aim to restore a full flying programme at Heathrow by the weekend. We will also offer a full programme at Gatwick and London City, as planned," it said.
BBC business editor Robert Peston said the decision created more uncertainty for passengers, and for employees.
"Although the company may regard it as a victory, it doesn't appear to have solved what is a very serious industrial relations problem," he said.
BA boss Willie Walsh said the strike action had been "unjustified" and he hoped the injunction would now give those involved in the dispute time to pause and reflect on the issues.
He said it was "time to move on and start rebuilding" and that he hoped to see "substantive progress in the days and weeks ahead".
Meanwhile, Unite joint leader Tony Woodley said "irrespective of how many technicalities the company found" it would not stop the union balloting its members again.
He added: "Its implication is that it is now all but impossible to take legally protected strike action against any employer who wishes to seek an injunction on even the most trivial grounds.
"Because of the far-reaching consequences of this injunction for all trade unions and indeed for our democracy, we are seeking leave to appeal immediately."
The company and union had been in talks at Acas during the day to try to find a way forward on disagreements over BA's cost-cutting plans.
Talks came to an end when the court injunction decision was known.
The first strike had been scheduled to begin on Tuesday, ending on 22 May, with the three further strikes planned to begin on 24 May, 30 May and 5 June.
BA had argued in court that Unite failed to follow the correct procedures in notifying its members of the result of the ballot.
The airline successfully won an injunction against the planned Christmas strikes in December last year.
However a spokesman for the Unite union said the decision had been "an affront to democracy in this country".
Unite's national officer Steve Turner said that "decent citizens" had voted in an open ballot which had then been ruled out by the judiciary.
He said the union would hope to be in the courts as early as possible, possibly on Tuesday.
In addition the union also said it had done everything possible to publicise the result of the ballot correctly, including posting it on the union website.
It said it had posted notices on crew locations at London airports, and used text messages and e-mails to get the strike ballot result across to members.
"We have no regrets," said Mr Turner. "We believe we complied specifically with the requirements of the law."
He added: "This is a global workforce of 12,500 people and we used tried and tested methods."
'Balance of convenience'
In his ruling the judge said: "I am unable to say it is sufficiently clear that the union took the steps required by law at the time they were required."
And he said that the "balance of convenience" in his view required the granting of an injunction.
BA and Unite are also still at odds over staff who have been disciplined or have lost travel perks because of their involvement in previous strikes.
Mr Walsh had ruled out intervening in disciplinary matters in order to call off the strike, saying that contingency plans were now in place, aimed at running the majority of flights during the strike dates.