Airlines lost at least $1.7 billion during the volcanic ash crisis, the industry said Wednesday as air controllers lifted all restrictions on German airspace, paving the way for more flights into some of Europe's busiest airports.
Giovanni Bisignani, the head of the International Air Transport Association, called the economic fallout from the six-day travel shutdown "devastating" and urged European governments to examine ways to compensate airlines for lost revenues, as the U.S. government did following the Sept. 11, 2001 terror attacks.
He said it would take three years for the industry to recover from the week of lost flying time that stranded millions around the globe.
Eurocontrol, the air traffic control agency in Brussels, said 21,000 of the continent's 28,000 scheduled flights will go ahead on Wednesday. Still, experts predicted it could take days -- even more than a week -- to clear a backlog of passengers from over 100,000 canceled flights.
"The crisis is petering out," said Brian Flynn, deputy head of operations. "The potential area where there could be any possible risk of some particles of ash cloud (has) dissipated throughout most of Europe."
But some restrictions remained in force over parts of Britain, Ireland and France.
"What we do have is one area which is southeast of the volcano which is where there is a detectable area of volcanic ash," he said.
Spain, meanwhile, has developed into a key emergency travel hub, arranging for hundreds of special flights to move over 40,000 people stranded by the travel disruptions. Its airports and airspace have mostly remained open throughout the crisis.
German aviation agency Deutsche Flugsicherung said the decision to reopen the country's airspace was made based on weather data, not economics. It said the concentration of volcano ash in the sky "considerably decreased and will continue to dwindle because of the weather conditions."
"Bremen, Hamburg, Hannover, Berlin, Frankfurt and Munich are open again," said Axel Raab, a spokesman for German air traffic control.
"We cannot say what it will look like in the next few days. If the volcano becomes active again, new closures might happen," Raab added. "This is a decision that was made based on meteorological data."
A test flight carried out by the German Aerospace Center found differing levels of volcanic ash at different sites over Germany. The highest concentration of volcanic ash was found over eastern Germany, but the report said its density was comparable to a plume of dust above the Saharan desert. The airspace above the northern city of Hamburg was entirely free from ash.
The center reported no damage to the airplane that flew the test flight.
A French weather service plane also took samples of the air Tuesday and found no volcanic ash problems either, according to French transport minister Dominique Bussereau.
Passengers, many of whom were stranded for days, welcomed the airport reopenings.
"It's good for us at least," Mats Tillander, a Swede at Frankfurt International Airport, who spent four days trapped in Texas, told AP Television News. But he was not sure who to believe in the dispute between airlines and governments as to whether the airspace closings were overkill.
"I don't know what's right and wrong," he said.
Airlines lost $400 million each day during the first three days of grounding, Bisignani told a news conference Wednesday in Berlin. At one stage, 29 percent of global aviation and 1.2 million passengers a day were affected by the airspace closure ordered by European governments, who feared the risk that volcanic ash could pose to airplanes.
"For an industry that lost $9.4 billion last year and was forecast to lose a further $2.8 billion in 2010, this crisis is devastating," Bisignani said. "Governments should help carriers recover the cost of this disruption."
He noted that the scale of the crisis eclipsed the events of Sept. 11, when U.S. airspace was closed for three days.
Flights resumed in many areas but the situation was anything but normal as airlines worked through an enormous backlog. Substantial delays were still expected across Europe, as airlines pressed to patch together normal flights with airplanes and crews scattered all over the globe.
In Iceland, there was no sign that the eruption at the Eyjafjallajokull (ay-yah-FYAH-lah-yer-kuhl) volcano was ending soon, according to Pall Einarsson, a geophysicist at the Institute of Earth Sciences in Reykjavik.
"We cannot predict when it will end," he said Wednesday. "(But) ash production is going down and is really insignificant at the moment."
At Heathrow's Terminal 3 outside of London -- home to many airlines including Virgin Atlantic and Air Canada -- no one was allowed inside the departures level until they had been checked by their airline to ensure they had a valid ticket. The departure boards still showed about half the flights as canceled.
Despite the uncertainty, passengers were optimistic that they would soon be moving. Juanjo Dominguez, a 25-year-old web designer from London, was at the airport for his afternoon flight to New York.
"I feel good, hopeful," Dominguez said. "I still think that things can happen from now ... I am still keeping my fingers crossed."
At the terminal's arrivals level, there was just a small trickle of passengers arriving from New York and Madrid.
In Spain, the airport in Barcelona -- near the border with France and thus a gateway to the rest of Europe -- took in flights from New York, Orlando, Vancouver, Paris, Nice and Rome. Airports in Barcelona and Madrid also chartered nearly 300 buses to get people to other cities in Europe, and Palma on the Mediterranean island of Mallorca handled 50 extra flights.
Bussereau, the French minister, predicted air traffic will be back to normal before the weekend as aviation authorities expanded the corridors where planes are allowed to fly. He estimated all of Air France's long-distance flights to and from France would fly Wednesday, and 60 to 70 percent of its mid-range flights.
Ryanair announced it will be resuming a "substantial proportion" of its normal services in northern Europe, beginning at 5 a.m. (0400GMT, midnight EDT) Thursday. Services to Ireland and Britain will begin Friday at 5 a.m.
Ryanair's chief executive Michael O'Leary warned, however, of substantial delays over the next few days "as all airlines struggle to clear the backlog of disrupted passengers."
Deutsche Lufthansa AG's chief executive on Wednesday welcomed the government's decision to reopen the skies. The quantity of ash from Iceland's volcano in German airspace is so low that there's "absolutely no danger," Wolfgang Mayrhuber told broadcaster ARD. "We will restart our system as quickly as possible."
Lufthansa, Germany's biggest airline, planned to operate some 500 flights on Wednesday, compared with 1,800 on a normal day.
Mayrhuber criticized how the flight disruptions were handled, shutting down wide swaths of Europe's airspace based on what he called were forecasts of questionable reliability.
"From the beginning, we had the suspicion that the forecasting model could not be all right," Mayrhuber said.
However, he said his company would not seek government compensation.
"We don't need a bailout, we don't need an umbrella," he said, declining to say how the shutdown would affect Lufthansa's bottom line.
Lufthansa is Europe's largest airline group by sales. It owns or holds stakes in carriers including Swiss International Airlines, Austrian Airlines and British Midland.
Associated Press Writers Slobodan Lekic in Brussels, Angela Charlton in Paris, Frank Jordans in Geneva, Jennifer Quinn and Sylvia Hui in London and Carlo Piovano in Reykjavik, Iceland contributed to this report.