A REVOLUTIONARY solar-powered aircraft touched down recently at Moffett Airfield, in the heart of Silicon Valley. No champagne corks were popped, however, for it arrived disassembled in the belly of a 747 cargo jet. The aircraft will be reassembled by the end of March and then begin flight tests. If all goes well, by May it should be ready to fly across America, stopping in four cities before landing in New York. However, this aircraft is just an experimental prototype for a much bigger exploit.