HEATHROW Airport has been branded "defeatist" for considering cancelling flights in advance of expected snowy weather.
The London airport said a decision would be made later today, based on the latest forecast, about whether any pre-emptive cancellations would be necessary.
Announcing flight cancellations before there is even any snow on the runways gives passengers advance warning before they travel to the airport, Heathrow said.
It also gives airlines more time to rebook people on to other flights.
But Boris Johnson, the Mayor of London, said it showed defeatism.
“This shows time and again the difficulty at Heathrow,” he said. “Every time there is a slight problem, Heathrow cannot cope.
“The answer is not a third runway, but another hub airport for London and the South-East.”
Former Transport Secretary Lord Adonis was also critical.
He told a Sunday newspaper: “The public will be expecting (airport operator) BAA to have learned the lessons from the last snow and to have the right equipment and training in place so we don’t see the chaos of the past two years.”
Because Heathrow is operating at full capacity, severe weather will always cause delays and cancellations, the airport says.
Airlines and air traffic control staff will take a decision today about whether cancellations will be necessary.
Snowfall of up to 10cm in parts of Britain is forecast for today and tomorrow, with commuters warned to expect travel disruption at the start of the week.
Snow and rain spread over western Scotland overnight and is expected to move south during the day, reaching parts of the Midlands by this evening, the Met Office said.
The temperature at Heathrow is expected to plunge to -1C tomorrow, while rural areas in places such as Lincolnshire could see the mercury fall to as low as -5C.
While a light dusting of snow will coat parts of England later today, a heavier dump is expected to land over north Wales, central England and northern England on Monday.
Most of the snowy areas will see between 2cm and 5cm settle, while places such as Yorkshire will see a coating of up to 10cm.
Cold weather will take hold of all the UK, but southern England and Wales are likely to be spared snow.
The Met Office has a level two weather warning in place until Tuesday covering the whole of England, alerting residents to ice, snow and bitter temperatures.
Nick Prebble, a forecaster for MeteoGroup, said: "A lot of people will be waking up to snow in Scotland this morning and there will be a light dusting in north-east England and Yorkshire.
"The snow will spread south-eastwards throughout the course of the day reaching Manchester, and overnight much of England will have snow flurries.
"But it will be throughout Monday when the heaviest snow falls, affecting central and east England and northern Wales.
"Those areas will see between 2cm and 5cm by the end of the day, but there is the potential for up to 10cm locally.
"It will be quite disruptive throughout the day before it clears on Monday night.” Britons have been stocking up on sledges and shovels following the first significant snowfall of the year in parts of the country yesterday.
The cold weather is likely to linger for the week, with the possibility of more light snow flurries in central and eastern England.
Online retailer Amazon said sales of sledges had surged by 600%, and customers were also investing in snow shovels.
"It's no surprise from looking at the weather reports that Amazon.co.uk customers are sensibly preparing by stocking up on snow shovels," said Xavier Garambois, vice president of EU retail.
"Sledging is undoubtedly the best thing about snow and, hopefully, a lot of fun will be had by all this weekend."