Holidaymakers face an anxious wait to see if travel plans will be wrecked after staff at BAA's six airports, including Heathrow, voted to take strike action in a row over pay.
No decision over the form or date of any strike will be taken before Monday, the workers' union Unite said.
But despite only half of the 6,185 Unite staff voting in the ballot, the union's leadership said BAA faced "a total shutdown" of its six airports - Heathrow, Stansted, Southampton, Glasgow, Edinburgh and Aberdeen. Of those who did vote, almost three quarters (74.1%) voted for strike action.
However, BAA said it did not believe the result provided "a clear mandate for strike action".
The earliest a strike could be called would be Monday August 23 - just ahead of the bank holiday weekend.
With the Unite members including firefighters and security staff, any walkout would have a devastating effect on UK air travel which has already been hit by a separate dispute involving British Airways' cabin crew, also represented by Unite.
Before today's result was announced, Prime Minister David Cameron said a strike would "do nothing but harm" and would damage business, jobs and tourism.
Unite national officer Brendan Gold and the union's national officer for civil aviation, Brian Boyd said the union would meet its shop stewards on Monday to decide what form of industrial action members would take.
Upset over what they describe as a "measly" pay offer from BAA, the two union leaders said there was still time for BAA to "get round the table and negotiate" and that it would "not take much" to sort out the dispute.
Asked if the union was trying to ruin people's holidays, Mr Gold said: "That's not our intention."
Asked if he had a message to the travelling public, Mr Gold said he hoped they would want to ask "why BAA has let this run on for four months (without any negotiation)".
Mr Boyd said strike action was a last resort, while Mr Gold said the aim was still to get a "negotiated settlement".
Both men denied any suggestion that the low turnout in the ballot weakened the union's position.
"The vote was substantially in favour of strike action among those who did vote," said Mr Boyd.
A BAA spokesman said: "We regret the uncertainty this vote has already caused our passengers and airline customers.
"We hope that the union will engage with us quickly to conclude an agreement.
"Fewer than half of those people eligible to vote have done so and we do not believe this result provides a clear mandate for strike action."
Mr Cameron, who made a speech today about the importance of tourism to the UK, said: "These sorts of strikes never achieve anything apart from damage - damage to business, damage to jobs, damage to the interests of tourists who want to come to visit Britain, or people who want to leave Britain and have a holiday overseas.
"I very much hope that they don't go ahead. They will do nothing but harm. We want to demonstrate that Britain is open for business."
Daniel de Carvalho, a spokesman for budget airline Ryanair, said:
"There is no justification for any strikes by these selfish and underworked Unite members at a time when traffic at BAA's airports is falling and they are even less busy than they were last year.
"Unite must not be allowed to blackmail ordinary passengers or their families by striking during the peak holiday season."
The Prospect union, which represents around 100 BAA workers based at Heathrow, Edinburgh, Glasgow, Southampton and Stansted airports, said 53% of its members had also voted in favour of strike action.
HOW THE STRIKE WILL BITE
Thousands are likely to be caught up in travel chaos after workers at BAA airports voted in favour of strike action.
- 6,185 BAA employees, including security workers, engineers, firefighters and support staff, were balloted by the Unite union.
- The total number of valid papers counted was 3,054.
- Of these, 74.1% were votes in favour of strike action and 25.9% were votes against it.
- The Prospect union, which represents around 100 BAA workers, said 53% of them had voted for strike action.
- Six airports - Heathrow, Stansted, Southampton, Glasgow, Aberdeen and Edinburgh - are expected to close for the duration of the strike.
- The strike will impinge on around 220 airlines which operate from these airports.
- Some 300,000 passengers are likely to be affected each day.
- Of these, 181,000 would have travelled through Heathrow.
- Up to 2,561 flights are likely to be cancelled for every day of action.
- Around 1,300 of these would have been to or from Heathrow.
- Up to 10,000 people employed by BAA could be affected by airport closures.