London's Heathrow Airport cancelled a fifth of flights overnight (NZ time) and airlines scrapped 40 per cent of flights to Paris's main airports as snow continued to blanket parts of Europe, with more forecast.
Heathrow Ltd, which is owned by Spain's Ferrovial, said the reduced schedule - amounting to around 250 fewer flights - would help it cope with the snowfall without making further cancellations.
The result is thousands of air travellers are stranded and there are reports of hundreds of people being forced to sleep in airport lounges while waiting for the weather to clear.
As snow continued to fall through, the airport operator said Monday's flight schedule would be cut by 10 per cent. That number could rise, depending on conditions at other European airports, Heathrow said.
The Paris airport operator, ADP, said airlines scrapped 40 per cent 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 but that delays and some flight cancellations were likely.
Weather forecaster the Met Office said snow was likely to continue into Monday (tonight, NZ time). As much as eight centimetres was expected in southeast England on Sunday, it said.
On average, some 1300 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.
"Many airports have plenty of spare runway capacity so aircraft can be spaced out more during low visibility without causing delays and cancellations," said Heathrow, whose owners have campaigned hard for capacity at the London hub to be increased.
"Because Heathrow operates at almost full capacity, there is simply no room to reschedule the delayed flights," it said.
Heathrow has spent £36 million (NZ$68m) 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 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 per cent 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, Ireland's Aer Lingus and Germany's Lufthansa 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.
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