1953?-

American aviator who piloted the first solar-powered airplane, the Solar Challenger, in 1981. Ptacek's plane, designed and built by Paul MacCready, was based on MacCready's previous designs for the first human-powered airplanes to fly a figure-8 course (winning the Kremer Prize) and to cross the English Channel. The Solar Challenger weighed about 210 pounds (95 kg) and was powered by over 16,000 solar cells. On his record-breaking flight, Ptacek flew 160 miles (257 km) at an average speed of nearly 30 mph (48 kph) at an altitude of 11,000 feet (3,350 m).