European airspace could be back to normal by Thursday as ash from the Iceland volcano dissipates rapidly, air traffic control bosses have said.
Brian Flynn, head of network operations for Eurocontrol, said it expects about 700 flights to be cancelled on Wednesday, mostly due to volcanic ash clouds over northern Germany.
But ash clouds could be dissipating because of the reduced amount of activity from the Grimsvotn volcano.
He said it opened up the possibility that the airline situation over Europe could return to normal on Thursday..
Some 29,500 flights were expected over Europe on Wednesday, including some 4,000 over Germany.
In Iceland, a volcano expert said that observers at the crater were reporting only steam, an indication that the eruption could be nearing its end.
"It's not over," said Pall Einarsson, from the University of Iceland. "But it's declining rapidly."
German air traffic control ordered all flights to and from Berlin's Tegel and Schoenefeld airports stopped at 11am on Wednesday. Airports in Bremen, Hamburg and Luebeck, had already been closed for hours, causing hundreds of flights to be struck. Controllers later re-opened Bremen and Hamburg.
While experts say particles in the ash could stall jet engines and sandblast planes' windows, many argue the flight bans are a massive overreaction by badly prepared safety regulators.
But, German transport minister Peter Ramsauer insisted the precautions were justified, and said that authorities were better prepared after the Eyjafjallajokull volcano eruption last year forced the closure of European air space for five days, stranding millions.