http://hardware.slashdot.org/article.pl?sid=09/07/12/1612230

"Dan Edwards, a student at NC State University, is attempting to break two records by creating an autonomous glider. The project goal is a 142-mile cross country flight and a 25-mile flight (with return) without human intervention. The glider finds thermal updrafts and automatically circles them to gain altitude, much like birds and insects do. Recently, the glider flew in the desert for 4.5 hours, covering 70.5 miles by itself using only air currents to stay aloft. Since the NC State demonstration vehicle does not have a motor, this shows real promise for unmanned aerial vehicles (UAVs) that actually have a motor, with possibilities of extending flight duration considerably. Combine daytime soaring with a solar energy system to charge batteries for the night, such as the 84-hour flight by QinetiQ's Zephyr, and you might just get an answer to flying for months on end. With this kind of endurance, the eye in the sky that the city of Lancaster is considering might be even more practical."