A solar-powered plane which can fly without fuel has taken off for its first 24-hour test flight before embarking on circumnavigation of the earth.
The plane, named Solar Impulse, left Payerne airfield in Switzerland on Wednesday.
Its pilot, Andre Borschberg, will take the prototype to an altitude of 27,900 feet by evening, when a decision will be made whether to fly the plane through the night using solar power stored in its batteries.
If he goes ahead, the plane will slowly descend to 4,920 feet before midnight, where Borschberg will stay until attempting a dawn landing.
Scientists working on the project hopes the plane, which has a 260-foot wingspan, will circle the globe using its 12,000 cells and take energy from the sun, the Daily Mail reported.
"The goal of the project is to have a solar-powered plane flying day and night without fuel," said team co-founder Bertrand Piccard.
He said the test flight - the third major step after its first "flea hop" and an extended flight earlier this year - will demonstrate whether the ultimate goal is feasible: to fly the plane around the world.
"This flight is crucial for the credibility of the project," said Piccard.
Piccard, who achieved the first non-stop circumnavigation of the globe in a balloon, the Breitling Orbiter III, in 1999, said that if successful, the next step will be an Atlantic crossing.
That will be done in a second, lighter prototype, involving new challenges and dangers, he added.