heathrow
A general view of Terminal 5 at Heathrow Airport prior to its official opening on March 14, 2008 in London, England. Getty Images / Dan Kitwood

More than 2,500 employees at Heathrow Airport in London, the busiest in the United Kingdom and Europe, still plan to strike Tuesday after agreeing to call off their protest action originally scheduled for Monday to give pay hike negotiations another chance.

The industrial action on Monday was announced by Unite the Union, Britain’s second largest labor union, which represents employees at London Heathrow. The airport also has to contend with a planned strike by British Airways pilots.

The two sides met throughout the weekend under the chairmanship of Acas, the government-funded body whose job is to help settle workplace disputes. Unite members, however, voted overwhelmingly against a pay raise offer Heathrow said was worth 7.3 percent over two-and-a-half years.

"Tomorrow's strike by Unite members working for Heathrow Airport has been suspended to allow for further talks at Acas tomorrow," said Unite in a statement released Sunday.

"Under the chairmanship of the conciliation service Acas, tomorrow's talks will involve senior directors from Heathrow Airport and senior Unite officials with the aim of averting a second day of planned strike action set to start at 00:01 and finish at 23:59 on Tuesday 6 August."

Unite said it won’t make any further comment while talks are ongoing.

Despite the reprieve, London Heathrow cancelled 177 flights but has now had to reinstate many of them, causing confusion and anger among passengers. Passengers are advised to check with their airlines to see if there were any changes to cancelled fights, said a Heathrow spokesman.

"We regret that passengers have been inconvenienced by this and urge them to contact their airline for up to date information on the status of their service," said the spokesman.

Swiss, Lufthansa, Qatar Airways, Flybe, and TAP Air Portugal were among airlines to have confirmed cancellations. It isn’t known if they’ll now reinstate flights.

British Airways, however, will reinstate flights from Heathrow on Monday. Air Canada plans to operate its full flight schedule on Monday. Aer Lingus and Etihad Airways confirmed they will reinstate their Monday flights, as well.

Virgin Atlantic hasn’t cancelled flights but will continue with its plan to move them from Heathrow to Gatwick. A spokeswoman for the airline said these services won’t revert back to the original London Heathrow schedule and will remain in place.