A plane powered only by the sun completed an 18-hour flight from San Francisco to Phoenix on Saturday, as part of journey to cross the United States. Adventurer Bertrand Piccard piloted the craft. Solar Impulse, as the vehicle is called, has a jumbo jet sized wingspan covered with 12,000 photovoltaic cells which capture sunlight to power the craft. Electrical energy stored in batteries is used when the sun isn't shining. The team behind Solar Impulse hope to circumnavigate the globe in 2015. More at NBC News.