On Wednesday, an erupting volcano in Iceland sent tons of ash into the air, shutting down airspace over Britain, France, Scandinavia, and other parts of Europe in what has been one of the largest airline stoppages ever during peacetime. British officials extended the grounding of flights to Friday afternoon, and other officials said they weren't sure when airspace would reopen. Several flights from England to the U.S. were turned back, and airports across Europe shut early. United Airlines canceled all flights from the U.S. to London, Paris, Amsterdam, Frankfurt, Brussels, and Moscow for Thursday and Friday. Eyjafjallajokull, the volcano, was still erupting as of 1 p.m. local time in London. Once the ash clears, however, airlines and airports will take a few days to sort things out. “For several days you’ll have crews and airplanes in the wrong places,” said an airline spokesman.