Unmanned Glider May Hold Secret To Perpetual Flight...

Engineers from the Australian Centre for Field...  ...als and adjusts its course, utilizing the thermal currents to stay aloft. Couple that ability with the techn...  ...ere the glider flies between high and lower speed air currents to keep it aloft when thermals aren't readily ava...

http://www.neatorama.com/2011/07/05/unmanned-glider-may-hold-secret-to-perpetual-flight/