Last ditch talks are to be held to try to avert a strike by thousands of workers at Heathrow Airport after they voted overwhelmingly to reject a pay offer.
Unite said its 4,000 members, including security guards, firefighters and engineers, rejected a revised deal by 88%.
A two day strike is planned to start on Monday, with a further 48 hour stoppage due from August 23.
Heathrow cancelled a number of flights on Monday and Tuesday before hearing the ballot result.
Unite said it would immediately enter talks at the conciliation service Acas and warned Heathrow against choosing to pay millions of pounds in compensation to airlines for cancelled flights rather than using that money to settle the dispute.
A Heathrow spokesman said: "We are disappointed that Unite has rejected the latest pay offer and will continue to seek an agreement at Acas.
"Unite is proceeding with its unnecessary strike action on 5th and 6th August and we regret that passengers looking to get away on well-earned breaks will be impacted by this.
"We have activated contingency plans which will keep the airport open and safe on both strike days. We expect security queue times to be slightly longer than normal and advise passengers to check our website for detailed information on how to prepare for their flights and when to arrive at the airport.
"As part of our plans, we are working with airlines to proactively consolidate flights and rebook passengers on to alternative services in advance. We also advise passengers to contact their airlines for the latest information, as well as follow our Twitter and Facebook accounts for further updates."
