The spreading cloud of volcanic ash from the Icelandic volcano, which is stretching across much of the northern Atlantic, forced the closure of airports across northern Spain and Portugal today.
Most flights between Europe and North America will be delayed today, the European flight control agency said. Flights will have to be rerouted north over Greenland or south over Spain to avoid the cloud, estimated to be nearly 2,000km long, that is stretching from Iceland to northern Spain, Eurocontrol said. This will increase flying times by about an hour in either direction.
"We assume that basically most of the transatlantic flights will have to be rerouted," Eurocontrol spokeswoman Kyla Evans said. "We expect substantial delays because of that."
About 600 airliners cross the Atlantic every day. About 40 per cent will be rerouted southward and the rest will skirt Iceland from the north.
Spain closed 19 airports in the northern part of the country today, airport operator Aena said. The closed
terminals include Barcelona, where the Spanish Grand Prix is being held tomorrow. Madrid airport is expected to remain open. Airports in southern France are also shut.
The government said over 400 flights would be cancelled, leaving almost 40,000 people stuck in airports stretching from La Coruna in the northwest to Barcelona in the northeast.
Air traffic was expected to be affected until midnight, at which time flights would gradually resume. However, the government said there was a chance the cloud could still be affecting Spain next week.
Just over 100 flights were canceled at mainland Portugal's three international airports because of the ash cloud, the national airport authority ANA said.
Marseille airport, the main French hub for Ryanair, said all the airline's flights had been cancelled.
Iceland's international airport is closed due to the cloud and is likely to remain shut for the rest of the day.
Until the Eyjafjallajökull volcano in southern Iceland stops its emissions, the key to the future course of Europe's ash crisis will be the prevailing winds. The eruption of the glacier-capped volcano has shown no signs of stopping since it began on April 13th. It last erupted from 1821 to 1823.
Since the ash is reaching altitudes of up to 10,000 metres, right in the path of most transatlantic flights, it will effectively block the usual routes. Eurocontrol said this would cause significant congestion, particularly in the airspace over Spain and Portugal where many of the diverted flights are heading.
A transatlantic flight from New York to Paris, which is normally about 5,800km long, could add on another 1,000 km - and an hour of flying time - by being diverted over the Iberian Peninsula.
Tracks across the Atlantic normally follow "great circles" - the shortest path between two points on the globe. They are determined each day by air traffic control centres on both sides of the Atlantic, generally depending on the jet stream from North America to Europe.
Planes flying the track system typically follow each other in 10-minute intervals and at altitude levels 300 metres apart, in order to maintain safety in airspace which is beyond the range of radar control.
Agencies