Flying solar

The Solar Impulse 2 is seen taking off at the Mandalay international airport, March 30, 2015. Picture taken with slow shutter speed. REUTERS/Soe Zeya Tun

Bertrand Piccard (L) celebrates with Andre Borschberg after the Solar Impulse 2 airplane, piloted by Borschberg, landed at Kalaeloa airport after flying non-stop from Nagoya, Japan, in Kapolei, Hawaii, July 3, 2015. REUTERS/Hugh Gentry

The Solar Impulse 2 airplane is greeted by hula dancers after it landed at Kalaeloa airport after flying non-stop from Nagoya, Japan in Kapolei, Hawaii, July 3, 2015. REUTERS/Hugh Gentry

Swiss pilot Andre Borschberg takes a selfie in the Solar Impulse 2 plane during the 7th leg of the round the world trip, June 1, 2015. REUTERS/Andre Borschberg/Solar Impulse

The "Solar Impulse 2", a solar powered plane, is seen on flight after taking off at the airport in the western Indian city of Ahmedabad, March 18, 2015. REUTERS/Amit Dave

The Solar Impulse 2, a solar powered plane, is parked in an inflatable hangar after an unscheduled landing at Nagoya airport in Japan, June 3, 2015. REUTERS/Thomas Peter

The Nagano mountain area is pictured by Swiss pilot Andre Borschberg in the cockpit of the Solar Impulse 2 plane during the 7th leg of the round the world trip, June 1, 2015. REUTERS/Andre Borschberg/Solar Impuls

Victorre Margaiaz (R) and Marion Perrey celebrate after the Solar Impulse 2 airplane, piloted by Andre Borschberg, lands at Kalaeloa Airport in Kapolei, Hawaii, after flying non-stop from Nagoya, Japan, July 3, 2015. REUTERS/Hugh Gentry

Solar Impulse 2, the world's first airplane flying on solar energy, is pictured en route to Ahmedabad, March 10, 2015. REUTERS/Jean Revillard/Handout via Reuters

The Solar Impulse 2 airplane, piloted by Andre Borschberg, lands at Kalaeloa Airport in Kapolei, Hawaii, after flying non-stop from Nagoya, Japan, July 3, 2015. REUTERS/Hugh Gentry

The Solar Impulse 2, a solar powered plane, circles above Nagoya airport in Japan before a planned landing, June 1, 2015. REUTERS/Thomas Peter

The Joetsu region in the West coast of Japan is pictured by Swiss pilot Andre Borschberg from the cockpit of the Solar Impulse 2 plane during the 7th leg of the round the world trip, June 1, 2015. REUTERS/Andre Borschberg/Solar Impulse

Swiss pilot Bertrand Piccard takes a selfie with his arm outside the Solar Impulse 2 plane during the 6th leg of their round the world trip, from Chongqing Jiangbei International Airport to Nanjing Lukou International Airport, Jiangsu province in China, April 21, 2015. REUTERS/Bertrand Piccard/Solar Impulse

The Solar Impulse 2 (foreground), a solar powered plane, sits on the tarmac after it landed at Nagoya airport in Japan, June 1, 2015. REUTERS/Thomas Peter

Swiss pilot Bertrand Piccard takes a selfie in the Solar Impulse 2 plane during the 6th leg of the round the world trip from Chongqing Jiangbei International Airport to Nanjing Lukou International Airport, Jiangsu province in China, April 21, 2015. REUTERS/Bertrand Piccard/Solar Impulse

A view of the Solar Impulse 2 on flight after taking off from Al Bateen Airport in United Arab Emirates, courtesy of Jean Revillard, March 9, 2015. Two Swiss pilots, Bertrand Piccard and Andre Borschberg, are attempting the first flight around the world in a solar-powered plane. REUTERS/Jean Revillard

Chinese policemen stand guard next to the Solar Impulse 2 plane after it landed at Nanjing Lukou International Airport, Jiangsu province, April 22, 2015. REUTERS/Stringer

Swiss pilot Bertrand Piccard takes a selfie in the Solar Impulse 2 plane during the 6th leg of the round the world trip from Chongqing Jiangbei International Airport to Nanjing Lukou International Airport, Jiangsu province in China, April 21, 2015. REUTERS/Bertrand Piccard/Solar Impulse

Solar Impulse 2 -a solar powered plane- takes off in Nanjing, China, May 31, 2015. REUTERS/Solar Impulse/Handout via Reuters

Photographers gather to take pictures of pilot Andre Borschberg (C) ahead of the take off of Solar Impulse 2 -a solar powered plane- in Nanjing, China, May 31, 2015. REUTERS/Solar Impulse/Handout via Reuters

"Solar Impulse 2" descends to land in Muscat, March 9, 2015. REUTERS/Jean Revillard/Handout via Reuters

Solar Impulse 2, a solar powered airplane attempting a round-the-world flight, flies over Nagoya Airport after taking off from the airport to Hawaii, at Toyoyama town near Nagoya, central Japan, June 29, 2015. REUTERS/Kyodo