European air traffic controllers said they expect 700 flights to be cancelled over Germany on Wednesday, almost one in 10 compared to normal daily traffic.
Brussels-based Eurocontrol said the disruption caused by an ash cloud that drifted from an Icelandic volcano across Britain before moving across the North Sea was focused on Germany.
"We are now expecting 700 flights to be cancelled today over Germany out of the normal 8,000 in Germany and 29,000 across Europe," Eurocontrol said in their regular Twitter update.
German Transport Minister Peter Ramsauer told public television ARD the fallout from the Grimsvoetn volcano eruption on Saturday was expected to improve later in the day.
Major German hubs in Frankfurt and Munich have not been affected.
Poland and Scandinavian countries are also expected to be affected.