Volcanic ash from Iceland's erupting volcano is again grounding flights in Europe as it continues to spread across the continent. Millions of travelers are being affected as flights are canceled and delayed. Civil aviation authorities say the disruption could last for several more days.
The European Air Traffic navigation and safety organization, Eurocontrol, says it expects further flight disruptions across European airspace as a plume of ash from the Icelandic volcano snakes through southern France, Switzerland and northern Italy.

The ash, stretching up from the surface to about 6,000 meters, has forced the closure of a number of airports in northern Italy. The Italian civil aviation authorities announced there would be no flying over a large part of the north of the country most of Sunday due to the ash cloud.

The airport in Venice, a major tourist destination, has so far been spared and is still open for travel. But other popular arrival points, like Pisa and Florence are closed. Passengers are being urged to check details of their flights before traveling to airports.

Millions of travelers in Europe and also those arriving and leaving the continent are being affected. Flight delays and cancellations are expected across Europe on Sunday as the ash cloud continues to disrupt international travel.
It is unclear how long the volcanic ash travel misery will last but authorities expect it could run into next week.

On a normal day, European air traffic control centers handle between 26,000 and 30,000 flights.

Until 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.

The five-day closure of European airspace last month due to the ash cloud forced the cancellation of more than 100,000 flights.

A plume of ash measuring up to seven kilometers (more than four miles) high had been detected at the Eyjafjoell volcano, said a statement late Thursday from the Icelandic Met Office and Institute of Earth Science.

"The eruption has changed back to an explosive eruption, lava has stopped flowing and most of the magma gets scattered due to explosions in the crater," said the statement in English.

"The ash plume rises high above the crater (4-7 km) and considerable ash fall can be expected in wind direction. No signs of the eruption ending soon."

The move prompted authorities to consider Thursday re-routing transatlantic flights and Ireland to shut airports for a third time this week.

"Ash production did increase last night and the ash plume is going higher now than the last couple of days," Agust Gunnar Gylfason, who monitors the eruption's progress at Iceland's Civil Protection Department, told AFP.

European airspace and airports across the continent were open Thursday, but intergovernmental air traffic control agency Eurocontrol said the ash cloud could mean transatlantic flights might need to be re-routed.

"Significant re-routing of westbound transatlantic flights to avoid the higher contaminated area is currently being discussed between the air navigation service providers concerned and Eurocontrol," the Brussels-based body added.

The area where concentrations of ash could still pose a risk to aircraft engines was lying to the north and west of Ireland, it said.

While the airspace above Ireland, Northern Ireland and Scotland was open on Thursday after having been shut for the previous two days, Irish authorities announced later in the day the new ash had forced them to shut airports again.

The Irish Aviation Authority (IAA) warned a "massive ash cloud" 1,000 miles (1,600 kilometres) long and 700 miles wide was hovering over the Atlantic and drifting into the country's airspace.

"While the northerly winds are keeping the bulk of the cloud out in the Atlantic, the increased size of the cloud is encroaching on Irish airspace along the west coast of Ireland," said the regulator in a statement.

Six airports would be closed, starting at midnight (2300 GMT) Thursday and continuing until 1:00 pm (1200 GMT) Friday. Among those shutting down were Shannon and Donegal, said the IAA.

The fresh disruption came after Europe's skies were closed for up to a week last month by the eruption of Eyjafjoell. It was the biggest aerial shutdown in Europe since World War II, with more than 100,000 flights cancelled and eight million passengers affected.

Gylfason said ash plume "had reached 30,000 feet (9,000 metres) for some time last night, and again this morning, due to an increase in explosive activity, but otherwise it's been around 18,000 and 20,000 feet."

At the strongest period of the eruption, Eyjafjoell sent a plume around 30,000 feet into the air, but scientists have stressed that the height of the plume does not necessarily reflect a particular quantity of ash.

On Tuesday, the plume contained about only 10 percent of the ash it held at the beginning of the eruption.

British Airways said Thursday that its passenger numbers fell by almost one quarter last month as a result of the flight bans prompted by the volcanic ash cloud.

Its total number of passengers slumped 24.5 percent to 2.081 million people in April, compared with the same month of 2009, it said in a statement.

The bodies representing most European airlines and airports have questioned the need for the unprecedented curbs, which affect millions of travellers.

Airlines that have carried out test flights say planes showed no obvious damage after flying through the ash.

EU Transport Commissioner Siim Kallas said he hoped 50% of Europe's airspace would be risk-free on Monday.

He said the current situation was "not sustainable" and European authorities were working to find a solution that did not compromise safety.

Mr Kallas also said EU transport ministers would hold a video teleconference on Monday to assess the situation. About 17 European countries have closed their airspace.

The flight bans came amid fears that the ash - a mixture of glass, sand and rock particles - can seriously damage aircraft engines. Airlines are estimated to be losing some £130m ($200m) a day.

ACI Europe - which represents major airports - and the Association of European Airlines issued a joint statement urging officials to reconsider the restrictions.

'Dangerous levels of ash'

"The eruption of the Icelandic volcano is not an unprecedented event and the procedures applied in other parts of the world for volcanic eruptions do not appear to require the kind of restrictions that are presently being imposed in Europe," the statement said.

Earlier, several airlines also questioned the curbs.

Peter Hartman, chief executive of Dutch carrier KLM, said there had been "nothing unusual" about a test flight carried out by the airline through the plume, and he hoped to "get permission as soon as possible to partially restart our operations".

Steven Verhagen, vice-president of the Dutch Airline Pilots Association, told the Associated Press news agency: "In our opinion there is absolutely no reason to worry about resuming flights."

Germany's two biggest airlines, Lufthansa and Air Berlin, also said they had carried out test flights without apparent damage, as did Air France.

Air Berlin spokeswoman Diana Daedelow told the BBC: "It is astonishing that these findings... have seemingly been ignored in the decision-making process of the aviation safety authorities."

A British Airways Boeing 747 completed a test flight through the no-fly zone at 30,000ft (9.1km) from Heathrow to Cardiff on Sunday.

While it encountered no problems, no loss of engine performance and no damage to windows, engineers in Cardiff were due to make a more detailed assessment of its engine overnight.

Earlier on Sunday, a UK Met Office plane went through the cloud and encountered dangerous levels of ash, showing that the issue is not whether the cloud is real and dangerous but whether its extent can be accurately mapped, BBC business editor Robert Peston writes.

One possible solution is to put observation planes in the sky, to give a more detailed picture of the location of ash concentrations, and the UK government is therefore trying to obtain more observation planes, from the military in particular, he adds.

Our business editor understands that BA fears it may not be allowed to fly normal services until Thursday at the earliest.

Worsening disruption

UK Transport Secretary Lord Adonis, said "urgent discussions" were taking place between European and international agencies to ease the chaos.

"We want to be able to resume flights as soon as possible, but safety remains my paramount concern," he said.

Weather experts say wind patterns mean the cloud is not likely to move far until later in the week.

Brian Flynn, head of operations at Eurocontrol - which co-ordinates air traffic control in 38 nations - dismissed suggestions the authorities were being over-cautious.

"With the overriding objective of protecting the travelling public, these exceptional measures have to be taken," he said.

Eurocontrol said there were only 5,000 flights in European airspace on Sunday, against 24,000 normally. There was a similar figure on Saturday. All but 55 of 337 scheduled flights by US carriers to and from Europe were also cancelled.