Malcolm McNiven and his son Luke show their boarding passes for their Virgin Atlantic flight back to Scotland at the Orlando, Florida, international airport. (AP)

London, April 20 (Reuters): European airports started to return to life today after five days cut off from the rest of the world by a huge ash cloud.

However, some airspace stayed closed after reports of a new plume from Iceland may be on its way. Italy, Switzerland and France reopened their airports early today, though many flights remained cancelled. In Italy, only a handful took off in the morning, mainly domestic flights. Hungary, Slovenia and Moldova also resumed flights.

But Britain’s National Air Traffic Service, which controls UK airspace, said much of Britain would remain closed to flights below 6,000 metres until at least midnight GMT after air traffic controllers warned a new ash cloud was headed for major air routes.

That included Heathrow, Europe's busiest airport, but not airports in the north. Airspace in Finland, Poland and parts of Sweden and Ireland was also closed. European aviation control agency Eurocontrol said today about half of scheduled air traffic in Europe was expected to operate — about 14,000 flights — up from a third yesterday..

The EU, which announced yesterday that its members had reached a deal to reduce the size of the no-fly zone from 0600 GMT today, acknowledged progress was slow.

“We know there are still a lot of problems for passengers on the ground,” spokeswoman for the executive European Commission Helen Kearns told a briefing. “We are faced with an unprecedented crisis. The disruption will continue over the week.”

Germany said it would maintain its no-fly zone until 1800 GMT, with exceptions.

Some airlines were taking advantage of the exceptions to fly. Flag carrier Lufthansa, for example, was flying on sight, which does not require air traffic control approval, to destinations like Seoul, New York and Lagos.

“We are operating about 200 flights today. That is the bulk of our long-haul flights, and domestic and European routes are significantly expanded today,” said spokeswoman Claudia Lange.

Yesterday’s EU agreement followed enormous pressure from airlines losing an estimated $250 million a day. “We were quite dissatisfied with the process that brought us here,” IATA spokesman Anthony Concil said of the delay before the EU ministers' deal.

“We need to find a better way for decision-making. Nonetheless, yesterday was a step in the right direction.”

The unprecedented disaster has stranded millions of people at the end of the busy Easter holiday season.

Many travellers have spent the past five days desperately trying to get home for school or work by road, rail and sea.

British businessman Chris Thomas, trying to get home from Los Angeles since Thursday, flew to Mexico City and then aimed to fly to Madrid and spend $2,000 to rent a car for the 14-hour drive to Paris. He was booked on the Eurostar Channel tunnel train to London, and then planned to drive four hours to Wales.

“It’s all a bit crazy but you have to err on the side of caution,” Thomas said.“Nobody wants to be on the first plane to go down in a volcanic cloud.” Gillian and Craig Robertson from Kilmarnock in Scotland were stranded in southern Turkey with their four-year-old son Jack and would likely miss a family wedding.