Travellers expressed disbelief as Britain's busiest airport axed half of all flights amid forecasts of dry weather following a nationwide blanket of snow.
The decision to ground planes at Heathrow for the second day running came as wintry showers ceased across the country.
Overnight up to 16cm of snow had swathed much of the country in a carpet of white, creating treacherous driving conditions and disrupting rail - as well as road and air - travel, while thousands of Britons ventured outside to enjoy the picturesque scenes.
But on Sunday, as the snow melted and the runways, taxiways and stands at Heathrow were cleared of snow, only 50% of the 1,300 scheduled flights were going ahead.
There were scenes of confusion and frustration at the west London airport where passengers faced a night sleeping on terminal floors.
A spokesman for Heathrow said its latest move was designed to minimise disruption as staff worked to clear a backlog of flights in the face of possible freezing fog. But forecasters said the airport was unlikely to experience particularly bad conditions.
Philippa Britton, from Kendal, Cumbria, said fellow travellers were amazed by Heathrow's decision. Ms Britton - who was transiting through London on a trip from Hong Kong to Manchester - said: "On the flight into London lots of people were astonished that so many flights had been cancelled. It's unbelievable. The runways seemed clear and they have cancelled the flights." Firs Alam, who was due to fly home to Tokyo on Saturday night, said he was having a "disgusting time" as he prepared to spend the night on an airport bench.
Their comments came as Heathrow insisted its "Snow plan" had worked "far better" than in previous years. "We took the decision with airlines and air traffic control yesterday to reduce the flight schedule in advance," a spokesman said. "By cancelling flights in advance airlines have been able to rebook some people on to flights that are departing, and passengers have had better quality information about whether they can fly or not."
Transport Secretary Justine Greening defended the airport's cancellation strategy and said bosses had taken the "right approach". "They are clearly trying to manage the airport and I think the most important thing is making sure that we put safety first," she told the BBC.
A spokesman for the Met Office said an amber warning of icy conditions which was in force for many areas of England earlier had been replaced by a "less significant" yellow warning advising people to "be aware" of icy stretches of road. Much of England remains under a cold weather alert of level three, which warns of "100% probability" of severe cold weather and icy conditions.
