A satellite captured the erupting of the Okmok Caldera volcano on Umnak Island in Alaska in July 2008. The volcano spewed both steam and ash. NASA/AP hide caption

itoggle caption NASA/AP

This infrared image shows ash spewing out of Iceland's Eyjafjallajokull volcano. It was taken April 17 by a NASA spacecraft. Hotter areas, shown in red, can be seen at the ash plume's base. NASA/JPL/EO-1 Mission/GSFC/Ashley Davies hide caption

itoggle caption NASA/JPL/EO-1 Mission/GSFC/Ashley Davies

Korean Air cargo planes sit idle on the tarmac at the Incheon International Airport in Incheon, west of Seoul, South Korea, on Monday. Every day, on average, 10,000 tons of goods are airfreighted between Asia and Europe. But none of that has moved for the past week after Iceland's volcanic eruption. Lee Jin-man/AP hide caption

itoggle caption Lee Jin-man/AP