LONDON/PARIS (Reuters) - London's Heathrow Airport cancelled a fifth of flights on Sunday and airlines scrapped 40 percent of flights to Paris's main airports as snow blanketed parts of Europe, with more forecast.
Air France predicted more cancellations on a similar scale for Monday.
Heathrow Ltd, 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.
As snow continued to fall through Sunday, the airport operator said Monday's flight schedule would be cut by 10 percent. That number could rise, depending on conditions at other European airports, Heathrow said.
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 British Met Office said snow was likely to continue 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.
"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 more capacity at the London hub.
"Because Heathrow operates at almost full capacity, there is simply no room to reschedule the delayed flights," it said.
Heathrow has spent 36 million pounds ($57 million) 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 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, Ireland's Aer Lingus and Germany's Lufthansa have also been affected.
France's SNCF rail firm announced delays of up to 40 minutes on many lines as drivers cut speed in a safety measure.
Some 25,000 homes lost power supply in southwestern France.
Emergency services were drafted in to rescue around 100 people from an urban train carriage that got stuck on a track which passes in open air over the Seine river in Paris, said Frederic Grosjean, a spokesman for city's emergency services.
($1 = 0.6304 British pounds)