While some are turning to biofuels as the energy source to keep future wings aloft, the team behind the newly unveiled Solar Impulse believes it can use sunlight to power their airplane-day and night. The unusual craft features solar-panel-covered wings as wide as those on a Boeing 747, but it weighs only as much as a typical car.

The team, led by Dr. Bertrand Piccard (co-record-holder for the first nonstop round-the-world balloon flight), has worked for six years to design and build the lightweight airplane, a design it hopes can spark interest in renewable fuel sources. During the day, power from 12,000 solar cells not only will run the aircraft's four 10-horsepower electric motors but also charge its batteries, which will provide power at night.

First flight of the Solar Impulse is expected before the end of the year in Switzerland, with a day/night flight to follow in 2010. Eventually, a follow-on model will tackle the challenge of global circumnavigation.