In anticipation of its historic round-the-world flight attempt, the route planned for Solar Impulse 2 (Si2) has been unveiled. The first solar-powered plane capable of day and night flight, the Si2 will spend 25 days aloft spread over a period of five months as it traverses 35,000 km (22,000 mi) with stops at 12 locations around the globe.

Tuesday's announcement by Bertrand Piccard and André Borschberg, the Swiss co-founders and pilots of Solar Impulse, provided the flight plan for the experimental aircraft as it attempts to circle the planet.

The Si2 will take-off from Abu Dhabi in the Persian Gulf in late February or early March, then proceed to Muscat in Oman, Ahmedabad and Varanasi in India, then to Mandalay in Myanmar, and finally Chongqing and Nanjing in China. From there, the plane will fly across the Pacific, stopping in Hawaii, and then three stops in the continental US, including Phoenix and JFK airport in New York City. The team says that the third location will depend on the weather. After New York, the Si2 will head for a stop in Southern Europe or North Africa before returning to Abu Dhabi.

With its 72-m (236-ft) wingspan, the Solar Impulse 2 is wider than a Boeing 747-8I, but weighs only about 2,300 kg (5,070 lb). Part of the reason for this is that it’s made out of carbon fiber employing a light single-ply technology used in competitive yachting, making it three times lighter than paper. Its four electric motors are powered by 17,248 solar cells 135 microns thick built into the wing and protected by a fluorine copolymer film, which feed banks of high-density lithium polymer batteries weighing 633 kg (1,395 lb). In flight, the plane is charged by the Sun during the day and powered by batteries at night for "virtually unlimited autonomy" and an average speed of 50 to 100 km/h (31 to 62 mph).

Currently, the Si2 is in the United Arab Emirate, where it will remain until take off. During the wait, the team says that it will be carrying out safety and flight tests, and speaking to industry representatives and engineering students about the flight. In addition, Piccard and Borschberg will spend layover time during the flight conducting airplane visits and promoting clean energy.

"Solar Impulse is not the first solar airplane, however it is the first able to cross oceans and continents – remaining in the air for several days and nights in a row without landing," says Borschberg. "But now we have to ensure the sustainability of the pilot in order to complete the route; Solar Impulse 2 must accomplish what no other plane in the history of aviation has achieved – flying without fuel for 5 consecutive days and nights with only one pilot in the unpressurized cockpit."

The video below outlines the construction of Solar Impulse 2.

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