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Solar explorer: Pilots begin epic five-month flight round the world powered purely by the sun with six-day stints at controls and temperatures ranging from -40C to 40C

The world's first solar-powered round the world flight which will last for five months and cover 22,000 miles began in Abu Dhabi overnight.

Aircraft Solar Impulse 2, which uses only solar energy to power its four engines, began the first leg of its ground-breaking journey at around 3.12am GMT this morning.

In total the plane will fly for 500 hours, cross three continents and span two oceans without using a single drop of conventional fuel. 

The pilots will have to fly alone for up to five days at a time, and say they will use yoga and self-hypnosis to stay occupied.

They aim to rest a maximum of 20 minutes at a time, repeating the naps 12 times over a 24-hour period. Goggles worn over the pilot's eyes will flash lights to wake them up.

Neither pilot will be able to stand in the cockpit while flying, but the seat reclines for stretching and its cushion can be removed for access to a toilet.

THE INCREDIBLE JOURNEY 

To break up flying day and night, Solar Impulse 2 will stop in 12 locations around the world 

After taking off in Abu Dhabi, capital of the United Arab Emirates, it will stop in Muscat in Oman and Ahmedabad and Varanasi in India.

From there, it will fly to Mandalay, Myanmar, before making two pit stops in China at Chongqing and Nanjing.

The solar-powered plane will then cross the Pacific Ocean via Hawaii.

A pit-stop in the south west of the US will be chosen depending on weather conditions, before the Solar Impulse 2 stops off at Phoenix and at JFK airport in New York City.

After crossing the Atlantic Ocean, it will make a stop somewhere in southern Europe, before undertaking the final leg of its journal to land in Abu Dhabi.

The 22,000-mile (35,000km) trip will span 25 flight days, spread over five months.

The two pilots, together with a crew of 80 technicians, engineers and a communications team were in Abu Dhabi for a fortnight before take off this morning conducting safety tests, test flights, and training.

During stopovers, people will be able to visit the airplane and Google Hangouts will be hosted.