British Airways (BA) cabin crew members of union Unite have "overwhelmingly" spurned the airline's latest offer.
Unite said 81% of the crew rejected the offer, which sought an agreement in the ongoing dispute over pay and working conditions.
Around 71% of the 12,000 BA staff members voted.
The union had openly called for its members to turn down the offer, saying it could not recommend the agreement.
British Airways said the rejection had been "clearly orchestrated".
The airline said it is "disappointed" at the outcome, and that the offer addressed all the concerns raised during 14 months of talks.
"We urge Unite to put an end to this unnecessary dispute and focus on the best interests of its members. There can be nothing positive to be gained from further strikes," said BA.
"Unlike other businesses and airlines, we have avoided compulsory redundancies. Cabin crew face no pay cut or reduction in terms and conditions - and remain the best rewarded in the UK airline industry.
"It is not too late for Unite to put an end to this dispute and support our recovery from two consecutive years of record losses and return to sustained profitability and job security for its members."
According to Unite, joint general secretaries Derek Simpson and Tony Woodley will meet on Monday to "discuss next moves", which could include further strikes.
Simpson and Woodley said: "BA management should take note of their own employees' strong rejection of their offer and immediately address the outstanding concerns.
"They should make no mistake that Unite is fully committed to supporting our members in furthering this dispute if no resolution is found."
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