Steady progress in zero emissions, solar-powered airplanes recently culminated in an unofficial endurance record of 54 hours by a remote-controlled airplane called Zephyr, built by Qinetiq. Another solar-powered airplane, the Solar Impulse, hit the headlines recently when the team building the airplane announced the launch of their prototype that will, they hope, carry a pilot around the globe in a series of flights.
Helios Prototype:Solar-powered flying wingImage courtesy of NASA