Solar Impulse whirred along the runway at Payerne in western Switzerland, reaching 35 km per hour as lone pilot Andre Borschberg gently lifted into clear skies at 6:51 am (0451 GMT). “Conditions are really beautiful up here, I feel great,” Borschberg said by radio some three hours into his planned 25 plus hour flight, as he cruised over the Jura hills in northern Switzerland at an altitude of 3,300 metres.

The Swiss pilot’s take off run took barely 90 metres, testimony to the light weight and giant airliner-size wingspan of the single seater craft, which relies totally on 12,000 solar cells and nearly half a tonne of batteries.

“This should be a great day if all goes well,” said team chief Bertrand Piccard, who made the first non-stop round-the-world flight in a balloon more than a decade ago.“It’s clear that this is something that is completely different at least for aviation, but it’s also something completely different to what has existed in our society,” he added.

“The goal is to take to the air with no fuel. The goal is to show that we can be much more independent from fossil energy than people usually think.”

The ground control crew were due to decide shortly before dusk whether Borschberg should press on with a pioneering flight through darkness and land at Payerne the next morning.

The go-ahead will depend on the sun’s ability to charge up Solar Impulse’s batteries in the daytime and the threat of strong high altitude winds, joint flight control chief and former astronaut Claude Nicollier said. “We’re confident the plane can do it.”
The overnight flight by the prototype built last year is the first major hurdle for the project since it started seven years ago, with the aim of flying around the world by 2013 or 2014.

The Solar Impulse prototype relies on the sun to power the engines and charge the batteries, in theory storing enough energy to last through some seven to eight hours of darkness.