Volcanic ash released from an eruption in Iceland Wednesday has grounded planes throughout Northern Europe, shutting down travel throughout the United Kingdom and all the way to Norway, Sweden, and Finland. The ash can interfere with airplane engines. The volcano blast, which led to flooding, forced 800 people from their homes in Iceland. No one will be flying into or out of the U.K. from noon until 6:00 p.m., according to a statement from the National Air Traffic Service. The ash has caused an air disturbance on a scale unseen since the terror attacks of September 11, 2001. Flights over Britain, Ireland, France, and the Nordic countries were halted, stranding tens of thousands of passengers. The ash cloud could continue for days or weeks, according to a scientist in Iceland, and would continue to pose threats to aircraft engines.