The NASA Helios UAV project met a goal this morning when the solar powered, autonomous robotic platform reached an altitude of 96,500 feet (18 miles). This exceeds its own previous record of 80,200 feet as well as the record for jet aircraft of 85,068 feet set by the SR-71 Blackbird. The final goal for the project is sustained flight at an altitude of 100,000 feet which would simulate flying in the atmosphere of Mars. CNN has a story on the latest flight (which, after 24 hours in the air, is still in progress as this is written). See also the NASA Helios background page and this excellent non-NASA Helios site maintained by interns working on the flight team.