Unite the union plans to take industrial strike action at Heathrow on Monday 5 and Tuesday 6 August, and Friday 23 and Saturday 24 August.
The airport has cancelled more than 170 flights on Monday and Tuesday because of the planned 48-hour stoppage by members of Unite.
UPDATE Unite the Union has said it will call off its planned strike at Heathrow to give it time to continue negotiating with the airport.
Union leaders met Heathrow management under the chairmanship of the conciliation service Acas on Saturday after discussions until 11pm on Friday. No update on the progress of the talks was provided by either party and they will resume on Sunday.
About 4,000 Unite members voted by almost nine to one to reject a pay offer Heathrow said was worth 7.3% over two-and-a-half years.