The Centurion solar-powered aircraft was one of an on-going series of vehicles designed for ultra-long-duration flight at high altitudes. The original vehicle was built by AeroVironment, Inc., in 1983 in a classified program called HALSOL for High Altitude Solar. After tests were completed, HALSOL was put into storage for a decade. In 1993, the vehicle was modified, becoming the Pathfinder. Five years later, another modification yielded Pathfinder Plus, with a wingspan increased from 98 to 121 feet.