Thousands of flights and train services have been cancelled across Europe because of snow and ice, leaving many travellers stranded.
Few flights were leaving London Heathrow, Europe's busiest airport, and one third of flights were cancelled in major hubs like Paris and Frankfurt.
Departures from Brussels airport were to be cancelled until Wednesday due to a lack of de-icing liquid.
Roads in a number of countries have been described as treacherous.
The UK, France and Germany were among the worst-hit areas, with forecasters warning of freezing weather all week.
There were severe delays on the Eurostar rail service between the UK and France and Belgium, and Thalys trains between France and Belgium were also affected as speed restrictions hit rail travel in England and northern France.
Lines of delayed passengers snaked for several hundred metres outside London's St Pancras station, and Eurostar - which is turning away even those with bookings - urged travellers to cancel or postpone their trips if possible.
Huge backlog
Further snowfalls in the Paris region caused serious problems for drivers, and heavy goods vehicles were barred from major routes.
Paris bus operator RATP cancelled a number of its services.
A concert by Lady Gaga at Bercy stadium in Paris was called off on Sunday night because a convoy of lorries carrying tour equipment could not get there.
German rail services were also affected. Heavy snow in Berlin caused problems for commuter trains and on the roads. Dangerous conditions were also reported on roads near Cologne.
Dutch authorities imposed a 50km/h (30mph) speed limit on a number of motorways, while icy, snowy roads also caused traffic problems across Sweden.
In Malmo, more than 100 commuter trains were cancelled because of the severe conditions.
As a sign of how bad conditions are, even in Moscow, where 9,000 snow ploughs are in action, some roads are at a virtual standstill.
In Italy, the airports at Florence and Pisa reopened after a weekend of cancellations.
More snow forecast
The schedules at Schiphol Airport near Amsterdam, Heathrow Airport and airports throughout the UK were littered with cancellations and delays.
Transport officials are struggling to cope with the current weather, compounded by the backlog caused by severe weather over the weekend.
Hundreds of passengers have been forced to spend the night at airports around Europe, stranded because of the weather.
In Britain, the Met Office has warned of more snow and ice in many parts of the country.
Southern England and south Wales were expected to have 5-10cm of snowfall and there were also warnings of further heavy snow for much of Scotland and north-east England, with up to 10cm of snow expected in northern Scotland.
The lowest UK temperature overnight, recorded in Chesham, Buckinghamshire, was -19.6C. Northern Ireland had another bitterly cold night, with -18C recorded at Castlederg in County Tyrone.
