The UK's busiest airport has been forced to cut its flight schedule by 20% as the country's transport network continues to struggle with freezing weather conditions.
Heathrow Airport in west London said it was reducing the number of flights scheduled for Sunday by at least a fifth after forecasters predicted another 2-6cm of snow and low visibility in the area.
Passengers are being urged to check with their airlines before travelling to the airport - where bosses are warning weather conditions at other European airports could further decimate schedules.
Passengers at Heathrow have been facing disruption after many were stranded on planes for seven hours or forced to spend a night on the floor.
More than 100 Saturday flights were cancelled and travellers complained about check-in queues of up to two hours as staff battled to clear a backlog caused by 400 cancellations on Friday.
Elsewhere, drivers are being warned of treacherous conditions after heavy snow on Friday across much of Britain turned to ice overnight.
A young woman from Peterborough was killed in a crash involving a number of vehicles shortly after 6pm on Friday, Lincolnshire Police said.
It is not known if anyone else was injured in the accident, which happened in bad weather on the A1 at Little Ponton, near Grantham.
Humberside Fire and Rescue said seven passengers were taken to hospital after a double-decker bus collided with two cars and ploughed into a garden.
In Edinburgh, a 16-year-old broke his leg when his sledge ran out of control and he plunged down a 150ft embankment.
The Met Office is forecasting more snow for Sunday and has issued yellow warnings for ice for large swathes of the country and a severe red warning for South Wales, which has experienced some of the worst weather.
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With more heavy snow possible on Sunday, the Highways Agency has said its fleet of snow ploughs and gritters will be out in force throughout the weekend.
Heathrow said its runways were open on Saturday with no restrictions, but services were still being disrupted following Friday's heavy snow.
Of 104 flights cancelled on Saturday, 100 were with British Airways, which has faced criticism for its handling of the disruption so far.
Husband and wife David and Janet Brindle, from Cumbria, branded BA's customer service and treatment of passengers caught up in the chaos as "appalling" and said some people had been close to tears.
The couple sat on a plane at Manchester airport from 9am until 3pm on Friday and have been stuck at Heathrow since missing their connecting flight to New Zealand.
Mrs Brindle said: "They got us off the plane but our bags weren't off. Not a single person came to tell us what was happening.
"Most people missed their connecting long-haul flights from Heathrow. We were advised to make our own way to Heathrow, so that's what we did.
"Nobody knew what they were doing. They couldn't tell us anything - they were quite rude, actually."
A British Airways spokesman said: "We have unfortunately had to make a number of cancellations today, mainly due to knock-on disruption from yesterday.
"So we've got a number of aircraft out of position and it's quite a complex operation to put that back together."
BA says it is offering customers who no longer wish to travel this weekend the chance to rebook their flight at a later date and providing refunds and overnight accommodation, or letters to make a claim, to those who could not fly.
Some passengers on British Airways flights told Sky News that they have spent up to seven hours on aircraft which have never left the runway.
Sky Reporter Clare Fallon, at Heathrow, said: "It's a surreal sight, there are hundreds of people on the floor trying to get some sleep because they are essentially stranded here. Some have told me they have been here since 11am yesterday morning.
"People feel very frustrated and stressed, and they don't understand how a relatively small amount of snow has been able to cause so much chaos."
A Gatwick spokeswoman said the airport was operating as normal on Saturday, with 505 flights scheduled and no knock-on effect from earlier bad weather.
In Northern Ireland, around 2,400 homes were left without electricity after the severe weather caused power cuts along the east Down coast.
The Highways Agency said several motorway lanes and major A roads had closed due to the snow and ice, as well as several crashes.
Drivers have been warned to be extra careful as freezing temperatures turn the snow to treacherous ice.
The deepest snowfall has been measured at 26cm in Sennybridge, Wales, although snow has been thawing in other areas and some train services have been returning to normal.
There have also been severe hold-ups for rail passengers, with many companies cancelling services to help them cope with problems caused by the weather.
Eurostar passengers faced delays of up to 30 minutes due to speed restrictions in France and Virgin Trains cancelled a number of services from London to Birmingham to Manchester, while others were delayed.
But while commuters have been facing misery, the winter wonderland scenes have brought joy to thousands of youngsters who got a long weekend after schools were forced to shut.
The weather also disrupted the sporting calendar, with six football matches in League One, eight in League Two and six in Scotland postponed.
Race meetings at Ascot and Haydock were also called off.
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Heavy snow is once again expected across the North East and Scotland, while other areas will see patchier coverage.
On Sunday, between 2-5cm of snow is predicted for the South East, the Midlands, East Anglia and Lincolnshire.
Darron Burness, from the AA, said commuting in the wintry conditions was "likely to test man and machine".
Those who decide to travel have been urged to travel prepared with a fully charged mobile phone, warm waterproof clothes, boots and a blanket, some food and drink, and have a torch, ice scraper, de-icer and a shovel.