A solar-powered plane its inventor hopes will lead to a non-stop round the world flight was unveiled today.
Solar Impulse has the wingspan of a Jumbo Jet but the weight of a small car.
Adventurer Bertrand Piccard who in 1999 co-piloted the first round-the-globe non-stop balloon flight said: "Yesterday it was a dream, today it is an aeroplane, tomorrow it will be an ambassador of renewable energies."
The plane will have test flights over the next two years, and based on their results a new version will be constructed for the big event in 2012.
The plane will fly day and night using almost 12,000 solar cells, rechargeable lithium batteries and four electric motors. It will not use an ounce of fuel.
But the maiden flight around the planet will take time.
With the engines providing only 40 horsepower, the plane will fly almost like a scooter in the sky. It will take off at the pedestrian pace of 22 mph, accelerating at altitude to an average flight speed of 44 mph.
The trip will be split up into five stages each five days long because of the cockpit, which was made non-pressurised to keep the weight down.
The first test flights will be later this year, with a complete night voyage planned for 2010.
"It will be like the Wright brothers," said the 51-year-old Mr Piccard, who comes from a long line of adventurers. His late father Jacques plunged deeper beneath the ocean than any other man, and grandfather Auguste was the first man to take a balloon into the stratosphere.
"We will start one metre above the ground, then three metres, then five metres," he said. "When that works, we'll be able to take it to altitude."
One thing a solar plane cannot handle is bad weather. Because the solar panels are needed for day flying and for charging the 400-kilogram lithium batteries that power the plane by night, it relies on sunshine.
Mr Piccard said the plane should also serve as an inspiration for inventors and manufacturers of everyday machines and appliances.
"If an aircraft is able to fly day and night without fuel, propelled solely by solar energy," Mr Piccard said, "let no one come and claim that it is impossible to do the same thing for motor vehicles, heating and air conditioning systems and computers."