[Solar Impulse HB-SIA, a] solar-powered aircraft making a landmark cross-country flight [piloted by Bertrand Piccard], successfully completed its first leg [on May 4], and will rest about a week in [Phoenix] Arizona before taking to the skies again. It's a little bit like being in a dream," Piccard told the Associated Press. The aircraft, running off solar cells and electric batteries rather than fossil fuels, ... travels at a leisurely 43 mph and cruises at a maximum altitude of 28,000 feet. Spokeswoman Alenka Zibetto [said] that the exact length of the stay would depend on weather. It is proving to be a popular attraction. Online registration for the Sunday slots -- with space for 150 people per hour -- filled up within a day, Zibetto said. The solar company SunPower [manufactured] the solar cells lining the 208-foot wingspan of Solar Impulse.