At the pace of a fast bicycle, a solar-powered plane took to the skies for its maiden flight Wednesday, passing an important test on the way to a historic voyage around the world - a journey that would not use a drop of fuel.

The Solar Impulse lifted off from a military airport at a speed no faster than 28 mph after briefly accelerating down the runway. It slowly gained altitude above the green-and-beige fields and eventually faded into the horizon as villagers watched from the nearest hills.

"There has never been an airplane of that kind that could fly - never an airplane so big, so light, using so little energy. So there were huge question marks for us," said Bertrand Piccard, who is leading the project. In 1999, he co-piloted the first nonstop round-the-world balloon flight.