The prospects for Sunday flights remained grim, with no improvement in sight for trans-Atlantic passengers, and with a plume of low-altitude ash continuing to float eastward over Spain and southern France.
Flights had to be rerouted north over Greenland or south around Spain to avoid the 1,200-mile (2,000-kilometer)-long cloud stretching from Iceland to northern Spain.
Approximately 600 airliners make the oceanic crossing every day. Around 40 percent were rerouted southward and the rest skirted Iceland from the north, according to Eurocontrol.
The disruptions to air traffic did not compare to the five-day closure of European airspace last month, which forced the cancellation of over 100,000 flights, stranded passengers around the world and causing airlines direct losses of more than one billion euros.
In Italy, the civil aviation authority ENAC said no flights would be allowed over a large swath of northern Italy on Sunday from 8 a.m. to 2 p.m. (0600 GMT to 1200 GMT) because of the cloud. Only the northeast corner of Italy was spared so far, leaving the airports of Venice, a heavy tourist destination, Trieste and Rimini open.
In Spain, 19 airports in the north, including the international hub Barcelona, were closed on Saturday.
The country's airport authority said more than 670 flights had been canceled by 14:00 (1200 GMT). Likewise, 125 flights in and out of Portugal were canceled up to noon local time (1100 GMT).
On a normal day, European air traffic control centers handle between 26,000 and 30,000 flights.
Until Eyjafjallajokul (pronounced ay-yah-FYAH-lah-yer-kuhl), the volcano in southern Iceland, stops its emissions, the future course of Europe's ash crisis will depend heavily on the prevailing winds. The eruption of the glacier-capped volcano has shown no signs of stopping since it began belching ash April 13. It last erupted from 1821 to 1823.
Aer Lingus canceled flights from the United States to Dublin, citing the exceptionally circuitous routes to get around the cloud.
Eurocontrol's forecast chart of volcanic activity for early Sunday showed a solid line of cloud extending from Greenland to the Azores and Madeira Islands in the mid-Atlantic, at altitudes up to 35,000 feet - right in the path of most trans-Atlantic flights. The Brussels-based air traffic management agency said the area of potential ash contamination was expanding in particular between the ground and 20,000 feet (6,100 meters).
“Depending on the winds, the ash could impact south France and possibly north Italy tomorrow,” said Eurocontrol spokeswoman Kyla Evans.
In Paris, Jerome Lecou, an engineer with the national weather service Meteo France, said that the Civil Aviation authority was doing a flight evaluation with an aircraft equipped with sounding devices to gather a maximum of information in order to determine whether the closure of some airports may be warranted.
He said it remained unclear whether the annual Cannes Film festival, which opens Wednesday, would be affected by the flight disruptions. Normally, stars, journalists and fans descend in hordes on the Riviera site.
A trans-Atlantic trip from New York to Paris is normally about 5,800 kilometers (3,600 miles) long. But rerouting could add on an additional 1,000 kilometers (600 miles), prolonging the flight by more than an hour and requiring about 10 percent more fuel.
Due to the congestion on the alternate routes, particularly over southern Portugal and Spain where many of the planes were being funneled, some trans-Atlantic flights were taking significantly longer. An Air France flight from Boston arrived in Paris Saturday with a delay of more than four hours.
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 centers 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 1,000 feet (300 meters) apart, in order to maintain safety in airspace which is beyond the range of radar control.
