Heathrow Ltd , which is owned by Spain's Ferrovial (FER.MC), said the reduced schedule - amounting to around 250 fewer flights - would help it cope with the expected snowfall without making further cancellations.2

"There is a high probability of around two to six centimetres of accumulating snow and low visibility at periods throughout the day," a Heathrow spokesman said.

"This will reduce the capacity of the airport and without action would cause significant disruption to passengers and flights."

The Paris airport operator, ADP, said airlines scrapped 40 percent of flights in and out of the two main airports on the outskirts of Paris, Charles de Gaulle and Orly, primarily reducing short-haul services.

London's smaller Stansted and Gatwick airports said they were operating as normal on Sunday morning but that delays and some flight cancellations were likely.

Weather forecaster the Met Office said snow was likely to continue throughout Sunday and into Monday. As much as eight centimetres was expected in southeast England on Sunday, it said.

On average, some 1,300 flights leave Heathrow daily. The airport, Europe's busiest, operates at close to full capacity after Britain's coalition government blocked development of a third runway in 2010.

Heathrow has spent 36 million pounds on upgrading its winter weather equipment since 2010 - a year that saw it face heavy criticism after it almost shut down when snow hit just before Christmas. It now has 130 snow-clearing vehicles.

More than 400 flights were cancelled on Friday, while on Saturday 111 flights, most of them operated by IAG's (ICAG.L) British Airways, were cancelled and hundreds of passengers spent the night in Heathrow's terminals.

BA said there had been a knock-on effect because many of its planes were in the wrong place after Friday's snow.

"Like other airlines at Heathrow we have complied with a request to reduce our schedule by 20 percent on Sunday and we continue to work with Heathrow Airport to help keep the airport running as smoothly as possible," BA said in a statement.

"We are doing everything we can to help customers whose flights have been disrupted by severe weather."

Services by Air France-KLM (AIRF.PA), Ireland's Aer Lingus (AERL.I) and Germany's Lufthansa (LHAG.DE) have also been affected.

France's SNCF railway company announced delays of up to 40 minutes on many lines as drivers were ordered to reduce speed as a safety measure.

Local media said some 25,000 homes lost power supply in southwestern France. (Additional reporting by Rosalba O'Brien in London, and Brian Love and Gerard Bon in Paris; Editing by Louise Heavens and Hans-Juergen Peters)

• A Permanent Economic Emergency