Photos: Soaring ambition for solar aircraft

After further refinements on the ground, the Solar Impulse is scheduled to make its first test flights by the end of 2009. The first flight will see the plane launch from its current home at the Dubendorf airport; the second will see it take off from the Payerne air base less than two hours away.

The aircraft will then take its first night test flight in 2010 to see if it can stay in the air for a 36-hour day-night-day cycle running solely on battery power without any fuel. From there, the next generation of the Solar Impulse, the HB-SIB, will make two test flights in 2012--the first across the Atlantic, and the second around the world in five legs over the course of four to six days.

Here an artist renders his impression of what the Solar Impulse might look like once it takes to the skies.