Strike action at Heathrow on Tuesday has been called off after the airport group and the union Unite reached a deal over pay.
Workers had planned to walk out on both Monday and Tuesday in a row over wages.
Strike action over the two days has now been averted but Heathrow said a walkout on 23 and 24 August is still scheduled to go ahead.
Unite and Heathrow have reached an improved pay offer which will now be presented to its members.
Fearing a strike on Tuesday, some airlines had cancelled flights - Heathrow has advised passengers to check whether those services will now go ahead.
On Sunday evening, when the first day of industrial action was suspended for Monday, a number of airlines chose to reinstate flights.
In total 16 cancelled flights on Monday.
A spokesman for Heathrow said: "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."
Some 4,000 workers had threatened to walkout over a pay deal which Heathrow said is worth 7.3% over two-and-a-half years.
Members of Unite will now have the chance to consider and vote an a new pay package.
Unite said that the strikes already announced for 23 August and 24 August "remained on the table until the result of the ballot was known".
A spokesman for Heathrow said: "Unite will now take an improved offer to its members and we remain hopeful that we can find a resolution and stop this disruptive and unnecessary threat of strike action."