EU expects 50 percent of airspace to be unaffected by volcanic ash Alvaro Barrientos / AP An unidentified passenger waits at Bilbao airport in northern Spain on Sunday after all flights were canceled. LONDON - European air traffic could return to about 50 percent of its normal levels Monday if weather forecasts confirm that skies over the half the continent are clearing of volcanic ash that has thrown global travel into chaos, the European Union said Sunday. Germany temporarily loosened some airspace restrictions before the EU announcement, allowing limited operations from Berlin, Hamburg, Hannover, Erfurt and Leipzig and some from Frankfurt and Hahn airports, but was closing them again Sunday evening. Other countries enforced closures on their national airspace through late Sunday, Monday or even Tuesday. The closures imposed after an Icelandic volcano begun erupting Wednesday have stranded millions of travelers. They are costing the aviation industry, already reeling from a punishing economic period, at least $200 million a day, according to the International Air Transport Association. EU Transport Commissioner Siim Kallas told reporters in Brussels that "it is clear that this is not sustainable. We cannot just wait until this ash cloud dissipates." Diego Lopez Garrido, state secretary for EU affairs for Spain, which holds the rotating EU presidency, said that "now it is necessary to adopt a European approach" instead of a patchwork of national closures and openings. "Probably tomorrow one half of EU territory will be influenced. This means that half of the flights may be operating," Lopez Garrido said about conditions Monday. Regulators need to take into account that several major airlines flew successful test flights without passengers over Europe on Sunday despite official warnings about the dangers of the plume, he said. The two officials did not immediately provide details on how the EU would work with national regulators to begin reopening airspace. KLM Royal Dutch Airlines said that by midday Sunday it had flown four planes through what it described as a gap in the layer of microscopic dust over Holland and Germany. The ash began spewing from an Icelandic volcano Wednesday and has drifted across most of Europe, shutting down airports as far south and east as Bulgaria. Air France, Lufthansa and Austrian Airlines also sent up test flights, although most traveled below the altitudes where the ash has been heavily concentrated. National air safety regulators have the right to close down a country's air space in cases of extreme danger. But they can also grant waivers to airlines to conduct test flights or to ferry empty airliners from one airport to another at lower altitudes not affected by the main ash clouds. Kallas called the problems spawned by the eruption unprecedented and said there were no EU-wide rules for handling such a crisis. Kyla Evans, spokeswoman for the European air traffic control agency Eurocontrol, said earlier in the day that it was up to national aviation authorities to decide whether to open up their airspace. The agency's role was to coordinate traffic once it was allowed to resume. "But there is currently no consensus as to what consists an acceptable level of ash in the atmosphere," said Daniel Hoeltgen, a spokesman for the European Aviation Safety Agency. "This is what we are concerned about and this is what we want to bring about so that we can start operating aircraft again in Europe." KLM said its received permission from Dutch and European aviation authorities for planes of various types to fly the 115-mile (185-km) flight from Duesseldorf in western Germany to Amsterdam's Schiphol Airport at an unspecified normal altitude above 10,000 feet (3,000 meters). They did not encounter the thick though invisible cloud of ash, whose main band has floated from 20,000 to 32,000 feet, the height of most commercial flight paths. Video Volcano fallout deals blow to fragile economy CNBC's Trish Regan offers economic analysis of the widespread impact caused of Iceland's volcano eruption. MSNBC The announcement of successful test flights prompted some airline officials to wonder whether authorities had overreacted to concerns that the tiny particles of volcanic ash could jam up the engines of passenger jets. The possibility that the ash had thinned or dispersed over parts of Europe heightened pressure from airline officials to loosen restrictions. "With the weather we are encountering now clear blue skies and obviously no dense ash cloud to be seen, in our opinion there is absolutely no reason to worry about resuming flights," said Steven Verhagen, vice president of the Dutch Airline Pilots Association and a Boeing 737 pilot for KLM. Meteorologists warned, however, that the situation above Europe remained unstable and constantly changing with the varying winds and the unpredictability was compounded by the irregular eruptions from the Icelandic volcano spitting more ash into the sky. CONTINUED : 'Normal conditions'1 | 2 | Next > http://www.msnbc.msn.com/id/36624082/ns/travel-news/ Video The dangers of flying in ash April 18: Rob Schapiro, a retired 747 pilot with 34 years of experience, says veteran pilots avoid volcanic ash clouds because of potentially catastrophic consequences.