Heathrow in last-ditch talks to avert Tuesday's strike
Officials from Heathrow and the Unite union are holding talks to avert strike action which would disrupt flights at the airport on Tuesday.
Monday's strike at the UK's biggest airport was called off late on Sunday and some airlines, such as British Airways, reinstated flights.
Even so, 16 flights were cancelled, including three by Lufthansa.
With a walkout of workers still scheduled for Tuesday, many more flights risk being cancelled.
Heathrow had initially cancelled 177 flights when the two-day strike action was announced.
A total of 676 flights were scheduled for departure on Monday. While 16 were cancelled, five were moved to other London airports.
'Hopeful for resolution'
Talks are talking place at the conciliation service Acas over the pay deal, which Heathrow says is worth 7.3% over two-and-a-half years.
A Heathrow spokesperson said: "Unite have chosen to postpone their strike action today. Strike action on Tuesday 6 August is still scheduled to go ahead.
"We are continuing talks with Unite today and we remain hopeful that we can find a resolution and stop this disruptive and unnecessary threat of strike action.
"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."
- Heathrow flights cancelled as support staff strike looms
- Heathrow strike action suspended on Monday - BA reinstates flights
Once Monday's strike was suspended, British Airways reinstated flights from Heathrow as did Air Canada, Aer Lingus, Etihad Airways, Flybe and TAP Air Portugal.
Virgin Atlantic moved flights from Heathrow to Gatwick, as did Qatar which also cancelled two flights.
'We can't magic a day back'
David Gee and his family thought they would be on the first day of their holiday on Monday.
Instead, Swiss cancelled their flights to Geneva in preparation for the strike action in Heathrow. They were rebooked on to a flight from City Airport on Tuesday.
"I do thank them for that," said Mr Gee.
But, he is unable to use train tickets from Geneva to Culoz in France which were not refundable. He will now have to rebook them - and incur additional travel costs to City Airport.
"Swiss staff confirmed over the phone that Swiss is not going to pay any compensation," he told the BBC.
"Heathrow airport - via their twitter messaging system - have said that we need to take the matter via our travel insurance and then - if needed - the insurance will contact them," he said.
Claiming on insurance could be difficult, he thinks, as "it is difficult to put a price on one day of holiday and the added train tickets are not much".
"If we claim, our premium is going to be increased for several years".
He is not seeking compensation but wants to cover the costs he has incurred.
"Heathrow won't give us the route [to applying]," he said.
"We can't magic a day back," he says.
Among the airlines to cancel flights were Lufthansa and Swiss, which scrapped three each.
Lufthansa had booked 365 affected passengers on alternative flights.
Airlines are now waiting to learn of any developments from Monday's talks with the union to decide what impact this will have on their schedules for Tuesday.
What are your rights if your flight is cancelled?
Heathrow's website contains information for travellers about what to do strike days. Strikes are also scheduled for 23 and 24 August.
It recommends passengers should contact their airlines, both in the days leading up to their flight and before setting off for the airport.
Passengers should check whether their flights out of Heathrow are affected or cancelled by contacting their airline. The airline would also advise on what to do next.
An airline is generally likely to offer a refund or alternative flights to the destination (possibly with other carriers) - although the latter may be harder for airlines during the busy summer period.
It is important for passengers to deal with the airline, rather than making their own alternative arrangements and trying to claim that expense later from the airline or a travel insurer.
'Allow more time'
If a flight has been cancelled owing to airport staff striking rather than those employed by the airline, it is unlikely that any extra compensation would be paid, as this would be considered "extraordinary circumstances" outside of the airline's control, the Civil Aviation Authority said.
The CAA added that the airport is not obliged to pay extra compensation directly to passengers, and whether the airport gives its customers (the airlines) compensation is a commercial issue between the two parties.
Heathrow said the airport may seem busier as usual as there will be extra staff as substitutes for those on strike.
It also urged passengers, particularly frequent flyers, to allow more time to clear security.
"Our advice to every passenger is to be in the terminal at Heathrow two hours before your scheduled departure for UK and European flights, and three hours for all other flights, even if you already have your boarding pass before arriving at the airport and are only travelling with hand luggage," Heathrow said.
Unite has about 4,000 members involved in the dispute.