British Airways cabin crew have voted to reject the company's latest pay offer.
The result of the Unite union ballot increases the possibility of strike action this autumn.
However, BA, which has already promised to fly 100% of its services if another staff walk out takes place, said the union had lost its mandate as less than half of unionised crew took part in the vote.
A little over 5,000 votes were cast, with 3,419 rejecting BA's offer.
Union bosses at Unite and Bassa will now meet to discuss their next move, which could include yet another ballot for strike action.
But a confident BA said in a statement: "We are encouraged by the result of this ballot which shows that 73 % of our cabin crew did not reject our offer.
"With only around a quarter of our cabin crew voting against the deal, support for Unite is ebbing away. The union has lost the moral authority to represent the views of our cabin crew.
"Such a low turnout raises serious questions for Unite and shows it does not have a clear mandate to reject our offer. We would urge them to come back to the table to sign the agreement and end the dispute.
"We have made a fair offer that includes two years of guaranteed rises in basic pay on top of annual increment pay increases and gives certainty to crew about their future earnings. There are no cuts in pay and our current Heathrow crew remain the best rewarded in the UK airline industry."
Some 22 days of strike action have already cost BA £150m this year.
The dispute between BA and crew started last year when the company announced cost cutting measures to cabin crew out of Heathrow.