In 1999, Bertrand Piccard traveled around the world in a balloon, without stopping a single time. Now, he's embarking on a journey across the United States — from San Francisco to New York — in an airplane with infinite gas mileage. The Solar Impulse HB-SIA is an electric aircraft powered entirely by solar panels, with 11,628 monocrystallane solar cells spread across its enormous Boeing 747-sized wing. Batteries, charged by those solar panels, take over in the evening.

On Friday, the craft began the first leg of its US voyage, from Mountain View, CA, to Phoenix, AZ — a 19-hour trip in the lightweight single-seater aircraft. One day at a time, with long breaks inbetween, the airplane will take two more months to reach its final destination in New York City. You can track the flight live.

Last year, the Solar Impulse flew from Europe to Africa in its first intercontinental flight, and the craft had its first international flight in 2011, but today the Swiss company's cofounder and chairman is showing the United States what solar power can do. The vision: an aircraft that can fly indefinitely without consuming any fuel whatsoever. This morning, we traveled to Moffett Field to witness the occasion.