Andre Borschberg, the pilot of an experimental aircraft which made history with the first round the clock solar-powered flight counted on a high-tech jacket, yoga and an uncomfortable seat to stop him nodding off.

"Andre is not allowed to sleep at all," Solar Impulse president Bertrand Piccard quipped as his 57 year-old pilot and chief executive tried to stay awake for 26 hours.

Had Borschberg, a former jet fighter pilot, nodded off or even slightly loosened his grip on the Solar Impulse flight over Switzerland, his jacket's sleeves would have vibrated if the aircraft tilted beyond five degrees.

An army of ground control staff also worked in shifts to help Borschberg keep the plane straight and level at less than 100 kilometres per hour.

With no automatic pilot, Borschberg needed to remain permanently alert.

The plane's wingspan the size of a jumbo jet combined with its light weight also made it extremely sensitive to a slight touch of the controls or wind turn, further requiring the pilot to remain in control.

To help him, the ground control mission - including a former astronaut and an ex NASA chief test pilot - was in constant contact and monitoring parameters such as altitude, angle of attack - up or down -, yaw and speed.

"You have to realise it's a very special airplane to fly, for its size - wings the size of an Airbus - for its weight you have to fly it extremely closely (on the controls)," said Borschberg by radio while he was flying above Switzerland.

Beyond the flight path, ground control was also monitoring the pilot's physical conditions in the narrow cockpit, which was not pressurised at high altitude.

He relied on an oxygen mask and was exposed to wild temperature swings reaching some minus 28 Celsius at 8,000 metres in broad daylight.

Confined to his seat, Borschberg snacked on high energy bars, home made sandwiches, French rice pudding (riz au lait) and coffee.

With no one to take over from him and no comfort of a toilet, Borschberg also has to relieve himself in plastic bags.

But with a few hours behind him, he said: "I feel great.

"When you learn flying you can do nights comfortably. I'm sure we'll get some winds but for the time being it's gorgeous," he told AFP as he enjoyed the daytime view of glimmering Swiss lakes and mountains.

The pilot later revealed that yoga exrcises kept his blood circulating, along with breathing exercises.

After the plane successfully landed Thursday following an overnight flight, Piccard revealed another detail that kept Borschberg from dozing off.

"We didn't install a first class (airline) seat, we installed a low cost seat," he said.

The overnight flight was the first major hurdle for the project since it was set up seven years ago with the aim of ocean crossings, transcontinental and round the world flights by 2013 or 2014.