Solar-Powered Plane Takes Off For Flight Across U.S.
Description:It's a plane powered by the sun --- and it took off on Friday from San Francisco for the first leg of an attempt to fly across the U.S. without any fuel. It's called the Solar Impulse and its battery is charged by energy collected from 12,000 solar cells built into the wings. The Solar Impulse can reach an average speed of 43 miles per hour.(0:47)