British Airways was facing the threat of a fresh wave of strikes by its cabin crew tonight after they voted heavily in favour of more walkouts in their bitter dispute with the airline.
Unite said its members voted by 5,751 to 1,579 to take further industrial action following 22 days of strikes last year which cost the airline more than £150 million.
The union pulled back from naming strike dates and will have to give seven days' notice of any action.
Unite's new leader, Len McCluskey, said: "For the fourth time in 13 months, British Airways cabin crew have voted overwhelmingly in support of their union and expressed their dissatisfaction with management behaviour. Indeed, the turnout and the majority on this occasion are much greater than in the last ballot.
"Surely BA management must now wake up and listen to the voice of their skilled and dedicated employees.
"This dispute will be resolved by negotiation, not litigation or confrontation, and it is to negotiation that BA management should now apply itself. We are ready."
News of the voting figures was revealed as the company completed its merger with Spanish carrier Iberia to create a new holding company, International Consolidated Airlines Group (IAG).
The bitter dispute started more than a year ago over cost-cutting but now centres on the removal of travel concessions from workers who went on strike, and disciplinary action taken against Unite members.
Unite said the turnout in the ballot was 75%, while the majority of those voting for industrial action was 78.5%.
The union balloted 10,220 cabin crew staff, 7,330 of whom returned valid papers.
Officials said the size of the turnout and the big majority in favour of industrial action showed the continuing anger and determination of the workers.
Speaking after a mass meeting of more than 1,000 cabin crew last week, Mr McCluskey said: "If the company believes they have broken the spirit of the cabin crew, they should have been at this meeting to witness the anger of people."
IAG will be listed on stock markets in London and Madrid on Monday morning.
The completion of the merger comes nearly 24 years after BA joined the London stock market in a high-profile flotation which was 11-times oversubscribed.
BA and Iberia will retain their brands as part of the initiative which is expected to save 400 million euro (£337.3 million) a year by its fifth year.
The new airline group will have 419 aircraft flying to 205 destinations and will be Europe's second biggest airline by market value after Lufthansa.
BA will also benefit through Iberia's strong presence in South America, where BA operates only a handful of routes.
Willie Walsh will step down as chief executive of BA to take up the same role at IAG in a move which will see his basic pay increase by 12% from £735,000 to £825,000 a year.
The ballot started on December 21 after hopes of a negotiated settlement to the deadlocked row collapsed despite months of talks.
Unite said the ballot was over a number of outstanding issues, including the immediate restoration of staff travel concessions, binding arbitration, through the conciliation service Acas, of all cabin crew disciplinary cases related to the original dispute and restoration of earnings docked from crew who were genuinely off sick during past strikes.
BA has pledged to run a full long haul service if there are any fresh strikes.
A BA spokesman said: "It is clear from this ballot result that Unite does not have the support of the majority of our cabin crew.
"Of our 13,500 crew, only 43% voted in favour of strike action in this ballot.
"Unite has lost about 2,500 cabin crew members since this dispute started, as crew have voted with their feet.
"Even with a smaller membership, the proportion of Unite members supporting disruption continues to fall, contrary to the union's claims.
"We urge Unite to return to the deal we negotiated, which guarantees pay rises for the next two years and secures terms and conditions for our existing crew that are the best in the UK industry.
"Tony Woodley shook hands on this deal in October. Unite said it would recommend it to members, but then reneged on its promise.
"This U-turn reflected the union's deep-seated internal divisions, especially its dysfunctional relationship with its crew branch, BASSA.
"It is time for Unite to listen to the majority of crew and to its members in other parts of the airline, who want an end to this dispute."
Bob Atkinson, travel analyst from travelsupermarket.com, said: "Groundhog day returns. British Airways customers are once more gearing up for a ride on the white knuckle rollercoaster controlled by Unite as they wait to hear when strikes will go ahead and if the airline can operate their flight.
"During the last strike BA managed to get a very high number of customers on their flights with minimum disruption, so what is the point of the union continuing this type of action?"