Ash clouds from Iceland's Grimsvotn volcano spread over Germany on Wednesday, forcing the closure of Berlin's airport and threatening to disrupt flight services over Europe. Plumes of volcanic ash that caused headaches to air travellers had forced the cancellation of hundreds of flights over Britain yesterday as winds blew the ash from Iceland's Grimsvotn volcano over Scotland. British authorities said, high-level densities of ash had cleared their airspace today and there were only scattered cancellations, mostly related to Germany bound flights. German air traffic control today said they would halt all flights to and from Berlin's Tegel and Schoenefeld airports, starting at 11:00 am local time. Airports in Bremen, Hamburg and Luebeck, have already been closed for hours, causing hundreds of flights to be stuck.