London's Heathrow airport hoped to operate more than 90 percent of flights today after days of delays and cancellations caused by ice and snow, but thousands of passengers still faced disappointment.

Some 200,000 passengers were expected to catch flights from the airport in the traditionally busy pre-Christmas period, a spokeswoman said.

But at least 120 flights were cancelled and authorities warned that the weather conditions of recent days had left many planes and crews out of position, so further delays were possible.

A Heathrow spokesman said: "We are extremely sorry for the disruption to people's journeys and we are working hard with airlines to return to a normal schedule."

British Airways, which is allowing anyone booked until December 31 to either rebook or receive a refund, said it hoped to operate all its Heathrow long-haul services today and the "vast majority" of short-haul flights.

Some terminals at Heathrow, one of the world's busiest airports, were turned into dormitories earlier this week as passengers unable to fly were forced to spend the night on luggage trays used as makeshift beds.

As conditions eased in southern England, Dublin airport had to shut until at least 1330 GMT after heavy snow covered the runway.

Scotland's main airport, Edinburgh, was open but reported delays and cancellations due to the weather.