London - Heavy snow disrupted European air travel over the weekend and stranded hundreds of drivers in their cars as far south as Italy as a white Christmas appeared increasingly likely for many places.
Britain was hit by more blizzards that shut its biggest airports on the busiest weekend for travellers before Christmas and hit road and rail traffic.
London Heathrow, the world's busiest international passenger airport, reopened Sunday after being closed for most of Saturday, but only a few flights took off. The situation was similar at London Gatwick where the runways had been closed for several hours the day before.
Flights were also grounded at Stansted and Luton airports near London, at Birmingham airport in Britain's second city and Southampton airport.
Eurostar, which operates high-speed passenger trains linking London with Paris and Brussels, was operating with speed restrictions that added up to an hour on journey times.
National rail routes and trunk roads were also affected. In Lancashire, northwest England, hundreds of people had to spend the night in their cars after an accident blocked the main north-south motorway.
Temperatures dropped as low as minus 17 degrees Celsius north of Norwich in eastern England. Gatwick registered minus 11 Celsius.
Sporting events were also hit, with several top flight football matches postponed, including Sunday's big English Premier League clash between title rivals Chelsea and Manchester United.
Frankfurt airport, Germany's busiest, cancelled some 490 flights Sunday due to heavy snow.
"Fresh snow is expected to fall around midday and could continue until midnight," a spokesperson said, predicting further flights from the around 1 300 scheduled to be axed during the course of the day.
Hundreds of stranded passengers had to spend the night on beds set up in the airport terminals, some for a second night in a row.
Flag carrier Lufthansa advised passengers to use the German rail service, which was also hit by delays and cancellations.
Four runways of Paris' main Roissy-Charles-de-Gaulle airport were closed on Sunday morning at 9:00 am as fresh snow fell, although two reopened by 10:30 am.
Before the closure all departing and arriving flights were between 30 minutes and an hour late.
The French civil aviation authority on Saturday told airlines to cancel at least a quarter of their scheduled flights to Roissy betweens 07:00 am and 15:00 pm.
Several hundred passengers whose planes were rerouted to Roissy because of the closure of London's Heathrow airport on Saturday spent the night in departure lounges.
At Paris' Orly airport one runway was cleared of snow early Sunday and flights suffered delays of an average 30 minutes.
Only a few bus services in the French capital were operating Sunday and none at all in the suburbs, a spokesperson for the city transport authorities said.
In the Netherlands several hundred people spent the night at Amsterdam-Schiphol airport, where air traffic continued to be severely disrupted on Sunday morning, an airport spokesperson told the Dutch news agency ANP.
In northern Italy the situation was improving after two days of chaos on the roads and in the airports in Tuscany.
Pisa airport, the hub of several budget airlines, which had been closed since Friday afternoon reopened on Sunday morning. Around 200 passengers forced to spend the night in the airport were issued with blankets and hot drinks.
Florence airport reopened late Saturday afternoon.
Stretches of motorway to the south and east of Florence, which had been paralysed from Friday under 20 to 40 centimetres (eight to 16 inches) of snow, had been cleared by Sunday morning.
In Belgium, around 1 500 people spent the night at Brussels airport. Most of them were on 18 flights bound for London rerouted because of Heathrow's closure.
Because London is outside the Schengen zone (passport-free travel within Europe), many passengers did not have the necessary visas to leave the airport and were not allowed to leave the transit lounge.
The snowfall even reached as far south as Algeria, where two people died in a road accident and traffic ground to a halt on several major roads.
The snowstorm that brought the chaos was moving slowly south over Europe, but the cold weather was expected to continue across much of the continent into next week.