An airline passenger waits on a chair in Terminal 5 at Heathrow Airport in west London Dec 20, 2010. Snow and freezing temperatures delayed flights across northern Europe on Monday, frustrating travellers trying to get away for Christmas and putting pressure on airline shares. [Photo/Agencies]

BERLIN/LONDON- Snow and freezing temperatures grounded flights and disrupted road and rail links across northern Europe on Monday, stranding travellers and closing schools.

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Only one of two runways at London Heathrow, the world's busiest international airport, was operating after a weekend snowstorm, forcing thousands to camp out in terminals. More than 1,000 flights at German airports in Frankfurt, Munich and Berlin were cancelled, disrupting business and Christmas holiday plans.

Freezing temperatures were expected to continue in Britain and Scandinavia for much of this week. Most of the rest of Europe is forecast to warm up in coming days, although a drop back to sub-zero levels is likely next week. For some the snowfall was welcome. Children's sledges were sold out in Germany.

"This much snow is only fun if you're a kid," said Berlin lawyer Katja-Julia Fischer, 42: "It's getting on my nerves."

A Brussels Airlines aircraft is de-iced on the snow-covered tarmac of Zaventem international airport near Brussels December 20, 2010. Brussels airport said on its twitter feed that it could not guarantee de-icing of planes after 1400GMT on Monday due to a shortage of de-icer caused by transport problems in France. [Photo/Agencies]

The severe weather has hit retailers at the height of Christmas trading. Britain's biggest department store chain, John Lewis, said sales fell more than 10 percent on Saturday.

Some online retailers were declining new orders or cancelling existing ones because of delivery problems, according to the industry body IMRG.

Northern France was also covered by heavy snow, disrupting road and rail traffic as Parisians braved clogged highways to reach their holiday destinations.