A solar-powered airplane took off on its first major test flight Wednesday morning, from an airfield in western Switzerland.
The flight of the plane, named Solar Impulse, comes ahead of plans to use a similar solar-powered plane to fly around the world in 2012.
"We want to demonstrate what can be achieved with renewable energy," Bertrand Piccard, the man behind the project, was quoted by the Swiss ATS news agency as saying.
The plane has the wing span of an Airbus A340, the weight of an average car, and is powered by some 12,000 solar cells.
The Solar Impulse - also the name of the project behind the plane - is "the first aircraft designed to fly night and day without fuel or polluting emissions".
The flight, aimed at testing the plane and discovering its vulnerabilities, was expected to last for about an hour and a half.
"With such a large and light plane never having flown before, the aircraft's flight behaviour remains unexplored," the project officials said in a statement before the flight began.
Previous tests of the plane have been on much smaller scales, involving seeing if the plane could get off the ground, but no extended airtime at significant altitude was attempted.