André Borschberg and his compatriot Bertrand Piccard will take turns piloting the single seater Solar Impulse 2 for 21,747 miles (35,000km) over 12 legs, including gruelling five- to six-day stints across the Atlantic and Pacific oceans. The entire journey will take five months.

Borschberg took the controls for the takeoff at Al-Bateen executive airport in Abu Dhabi early on Monday. Its first destination is Muscat in Oman.

The pilots will endure roughly 250 hours each inside a narrow cockpit with no oxygen or temperature control. Temperatures outside will range between -40C to 40C.

Falling asleep for long periods will be impossible as the flight will need constant attention. Piccard and Borschberg will survive on 20-minute naps every two to four hours.

The pilots will practise yoga to stave off the physical discomfort of remaining confined to a seat for days at a time. But Borschberg said the biggest challenge was maintaining concentration.

Piccard, who is a psychiatrist as well as being part of the team that in 1999 first circumnavigated the globe non-stop by balloon, has taught himself and Borschberg techniques of self-hypnosis and meditation in order to maintain concentration.

“Time is not so important anymore,” said Borschberg. “You have plenty of time and the only way to cope with this duration is to be in the present moment. If you start thinking about how many hours left until you get to the destination you get crazy. So the only way is to be present ... In some ways it’s almost a spiritual experience that we are going through.”

-The Guardian