Heathrow workers have backed industrial action in a row over holiday pay and imposed cuts to terms and conditions, Unite union said today.
Security staff, engineers and firefighters were balloted, with the union saying members across all three groups had backed strikes.
However, the security guards, which make up the largest number of workers considerably, would not be able to take action legally, as they missed out on the necessary 50 per cent turnout threshold by two per cent.
The union's reps will meet in the coming days to discuss the next steps. Unite warned last month that the pay row could lead to industrial action over the busy Christmas period, after around 4,000 workers rejected the firm's holiday pay offer and imposed cuts to terms and conditions in a consultative ballot.
Read more: Get ready for another Tube strike
Wayne King, Unite regional officer said today:
Today’s result should be a massive wake-up call to Heathrow bosses. They need to recognise the sizeable discontent that exists among its staff and start negotiating with the union to repair the serious breakdown in industrial relations.
He added: "Unite reps will be meeting in the coming days to discuss next steps, in the meantime we are urging Heathrow bosses to heed this warning and get back around the negotiating table to hammer out a deal on the outstanding issues."
The union had previously called on the airport to get back around the table "to reach a genuinely negotiated settlement", or risk "major disruption" during the festive period.
A Heathrow spokesperson said:
Following a formal ballot, Heathrow colleagues working in security who are members of Unite the Union, have returned a verdict that has not reached legal thresholds required for strike action. They have failed to meet the numbers needed on turnout and also failed to secure enough votes from those in favour of action at the airport.
We are proud of our record as a good employer and the rewarding careers we offer for local people. We want to continue to build partnerships will all our unions and we remain open to discussions with Unite and its members.
The airport had previously pledged to have "robust contingency plans in place" to ensure the airport continues to operate safely and minimise disruption to the airport's operation, should industrial action go ahead.
Meanwhile, the London Underground is also braced for a strike threat.
Earlier this week, the Rail, Maritime and Transport (RMT) union declared an official dispute with Transport for London in a row over career progression on the Night Tube. The RMT said it will ballot drivers over industrial action.