Heavy snowfall and bitterly cold weather continues to hamper travel across much of northern Europe, raising fears that some holiday travelers may not reach their intended destinations. Fresh snowfall forced officials at Germany's Frankfurt airport to suspend flights for several hours today, causing backups at the country's largest hub for air travel.London's Heathrow airport is operating only about a third of its flights. In Paris, aviation officials are trying to clear a backlog of flights. The French news agency says 3,000 people slept in terminals at Paris's Charles de Gaulle airport on Sunday. Forecasters have predicted abnormally bad weather through the week, as the continent endures its snowiest, coldest weather in decades.