Solar Impulse, the Swiss bid to make the first solar-powered flight around the world, rolled out its prototype on Friday at an airbase near Zurich and powered up the engines.

All four sun-fuelled electric motors were switched on for the first time under open skies after the completed high-tech plane was pushed out of the hangar.

"With its engines running at full power, it gave the impression of wanting to get off the ground straightaway... but it won?t be long now before we release the brakes and let it roll its first few metres," said Andre Borschberg, co-founder and chief executive of Solar Impulse.

The ultralight single seater with the wingspan of an Airbus A380 airliner is being prepared for a maiden flight over the coming weeks when weather conditions allow.

Solar Impulse staff said the slender craft, which only weighs as much as a medium-sized car (1,600 kilogrammes, 3,527 pounds), needs particularly clear conditions and less than a light breeze (three knots) for its first excursion in the air.

It is due to make a few airborne hops down the runway at the Dubendorf airbase before December 20.

Borschberg said the aircraft was venturing into new flying territory.

"Compared to its weight and size, it is lighter than the best performing gliders," he explained.

The prototype, which is slightly smaller than the craft that is expected to fly around the world, was first unveiled while it was being built in its hangar in June.

It is primarily aimed at testing the cutting edge technology used to build and control the aircraft, and to fly through the night.

A first non-stop 36 hour flight through darkness is planned in Switzerland from spring 2010, with the prospect of a five stage flight around the world in 2012.