Holy smokes! An Icelandic volcano eruption that caused flooding and forced hundreds to escape high water on Wednesday grounded 25 percent of European air traffic on Thursday. An ash cloud as high as 33,000 feet continues to blanket the United Kingdom, Scandinavia, and large swaths of Northern Europe, currently hovering near the most common flight paths from the U.S. East Coast to Europe. Drifting bits of rock, glass, and sand have the potential to shut down plane engines altogether. The widespread cancellations are the most drastic since the September 2001 terrorist attacks in the U.S.: Britain closed all airspace until at least 7 a.m. local time Friday; France halted all flights to Paris and 23 of its airports until at least 10 a.m. local time Friday; Ireland grounded all planes for at least 8 hours; and airlines around the world are coping with cancellations from Heathrow Airport, which sees more than 180,000 flyers each day. In the U.S., the Federal Aviation Administration is trying to re-route some flights around the colossal plume, but European officials say it could take days to sort out the mess.