Some of Europe's airlines and airports have called into question whether the mass restrictions imposed on the continent's airspace, due to volcanic ash in the area, are necessary.

Millions of travellers have been stranded by the cancellations; however, some airlines have made test flights to see if there were any immediate effects on jets after flying through ash. Authorities fear that the ash can cause vital aircraft parts, such as the engines, to fail in-flight.

Three large airlines — KLM, Air France, and Lufthansa — have already made test flights. <name>Ulrich Schulte-Strathaus</name>, the head of the Association of European Airlines (AEA), commented: "Verification flights undertaken by several of our airlines have revealed no irregularities at all; this confirms our requirement that other options should be deployed to determine genuine risk."

KLM, meanwhile, said that it will allow three freight planes to make flights to Asia, and had transferred seven passenger planes from Duesseldorf, Germany to Amsterdam, without any travellers.

"We observed no irregularities either during the flight or during the initial inspection on the ground. We hope to receive permission as soon as possible after that to start up our operation and to transport our passengers to their destinations." said KLM chief executive <name>Peter Hartman</name>.