Experimental solar-powered Swiss plane, laptop batteries included, on 24-hour test flight

GENEVA - An experimental solar-powered plane whose Swiss makers hope someday to fly around the globe soared into uncharted territory Wednesday - the cold, dark night. The team of adventurers and engineers behind the Solar Impulse project are already celebrating an aviation milestone for the longest solar flight after keeping the single-seat prototype aloft for almost 15 hours. As the sun set, technicians hoped the Solar Impulse's laptop batteries - charged from the 12,000 solar cells fixed to the wings and body - would keep the four-engine plane engines airborne through the night. Piccard said the night flight was a key step toward achieving that ultimate feat. Borschberg was circling in Swiss airspace, first at 28,000 feet (8,535 meters) and then gently easing down through the night - always within gliding range of Payerne airport, so he can land if the plane runs out of energy, Piccard said. Piccard said the test flight - the third major step after its first "flea hop" and an extended flight earlier this year - will demonstrate whether the round-the-world trip is feasible. Piccard, who achieved the first nonstop circumnavigation of the globe in a balloon, the Breitling Orbiter III, in 1999, said the next major step will be a solar Atlantic crossing.