Reporting from London — Air travel in Europe took a few halting steps toward recovery Tuesday, even as a new cloud of volcanic ash from Iceland began drifting east, threatening further flight delays.
Passenger jets took off to cheers in cities across Northern Europe, where stranded travelers had waited for days to get home. The continent-wide aviation agency Eurocontrol said it expected 13,000 flights through European airspace Tuesday, which would be the most since Friday. The usual daily traffic load is about 28,000 flights.
But the resumption of service was piecemeal as travel restrictions over various parts of the continent stretched into their sixth day. In Britain, some departed from Scotland and Northern England, but in the south, London's Heathrow airport, one of the world's busiest hubs, remained closed for most of the day. Authorities allowed it to reopen late Tuesday.
Meteorologists said more ash and grit from the Eyjafjallajokull volcano was heading toward the European mainland, raising the possibility of extended or renewed flight bans.
In Germany, Lufthansa Airlines ran intercontinental flights out of various airports, many of them bound for the United States. The carrier said it planned to do so again Wednesday and would fly some domestic and European routes.
Air France said it was able to resume 95% of its long-haul flights and 25% of its medium-haul routes Tuesday. Long-haul service should be fully restored Wednesday, as well as nearly all medium-haul flights and half of its domestic ones, the airline reported.
Planes also landed and took off Tuesday from Amsterdam's Schiphol airport, another busy European hub.
"There has been a progressive opening of routes and of airspaces," said Brian Flynn, deputy head of operations at Eurocontrol.
The agency said all European airspace above 20,000 feet is open, allowing jets to fly over countries that still maintain restrictions on takeoffs and landings. About 75% of the continent has no airspace restrictions.
The shutdown of Heathrow for most of Tuesday, however, meant that thousands of luckless travelers remained earthbound. Aviation officials lifted the embargo on Heathrow and all other British airports late Tuesday, saying test flights and further analysis by plane manufacturers indicated that regular flights could resume.
Clearing the backlog is likely to take days.
"We've now got to start the difficult task … of getting our stranded customers back home," said British Airways Chief Executive Willie Walsh, who had been increasingly critical of the continued closure of most of British airspace. "This has been a difficult period for everybody."
The British government had said Spain, relatively untouched by the travel crisis, had offered to make Madrid a hub for Britons unable to fly home directly. From the Spanish capital, buses were to deliver passengers to ports from which they could catch ferries to Britain.
A British warship picked up troops returning from Afghanistan and about 200 civilians from the Spanish seaside city of Santander. Two other navy ships were also to transport stranded travelers in the next few days.
The gradual easing of the lockdown of European airspace came amid heavy pressure by airlines to get their idled fleets back in the air. Aviation authorities said safety remains of paramount concern, but growing gaps in the ash cloud allowed for a rollback of some of the flight restrictions.
Eyjafjallajokull continues to erupt, belching dust and glass particles that could cause jet engines to seize up. More grit has been creeping south and east, and air traffic regulators say restrictions on airspace could be revived.
Meteorologists say, however, that the most recent plumes of ash are not reaching such high altitudes as before and that winds strong enough to disperse the ash could pick up in a few days.