Proteus
This odd, tandem-wing research aircraft, built by Scaled Composites in 1998, was designed to serve as a temporary communications satellite. First flown in the late 1990s, the Scaled Composites Model 281 Proteus tested many technologies for use in high altitude telecommunications relays for the military and research institutions. Due to its incredibly efficient airframe, the Proteus could cruise at 65,000 feet for over 18 hours. All at a fraction of the cost of a satellite in low earth orbit. Of course, the introduction of unmanned drones made such piloted aircraft unnecessarily expensive for long-endurance missions like these and the project was scrapped.