Solar Impulse is ready for its toughest challenge yet: Starting May 1, the sun-powered plane will begin a long, slow trip from California to the other side of the United States, reports the Mercury News. With four 10-horsepower engines, the Solar Impulse flies at 35 miles per hour—that's with the wind at its back. Factor in four stops of up to 10 days each along the way, and the journey turns into a long one: The plane is expected to land at JFK in early July.
"This airplane could do it nonstop," says co-pilot and project CEO André Borschberg. "But because the pilot is not as sustainable as the technology, we have limited ourselves to 24-hour flight duration." In development since 2003, the Solar Impulse first flew for 24 hours in 2010, then from Madrid to Morocco last year. If the cross-America flight goes well, Borschberg says they will try taking their solar plane around the world in 2015. "It's a beautiful dream, but in terms of practical application, I think we're still about 15 years away," said one solar cell developer. (Read more Solar Impulse stories.)