A view of the Solar Impulse 2 on flight after taking off from Al Bateen Airport in United Arab Emirates, March 9, 2015. (Photo by Jean Revillard/Reuters)

Ground staff prepare to push the Solar Impulse 2, a solar powered plane, into a hangar after it landed at the airport in the western Indian city of Ahmedabad, March 11, 2015. (Photo by Amit Dave/Reuters)

Solar Impulse 2 takes-off for its fourth flight from Varanasi to Mandalay, Myanmar with Bertrand Piccard at the controls, March 18, 2015. (Photo by Jean Revillard/Reuters)

The Solar Impulse 2 prepares to take off at Al Bateen airport in Abu Dhabi, March 9, 2015. (Photo by Ahmed Jadallah/Reuters)

The Solar Impulse 2 is seen before take-off at the Mandalay international airport, March 30, 2015. (Photo by Soe Zeya Tun/Reuters)

Solar Impulse 2, the world's first airplane flying on solar energy, is pictured en route to Ahmedabad, India, March 10, 2015. (Photo by Jean Revillard/Reuters)

The Solar Impulse 2 takes off at Al Bateen airport in Abu Dhabi, March 9, 2015. (Photo by Ahmed Jadallah/Reuters)

Ground staff remove the cover from the wing of the Solar Impulse 2, a solar powered plane, inside the hanger at the airport in the western Indian city of Ahmedabad, March 11, 2015. (Photo by Amit Dave/Reuters)

Solar Impulse 2 descends to land in Muscat, Oman, March 9, 2015. (Photo by Jean Revillard/Reuters)

Pilot Bertrand Piccard (L) and pilot Andre Boschberg are welcomed after landing Solar Impulse 2, the world's first airplane flying on solar energy, in Ahmedabad, India, March 10, 2015. (Photo by Jean Revillard/Reuters)

A solar-powered plane takes off from Jiangbei International Airport in southwest China's Chongqing Municipality, Tuesday, April 21, 2015. The Solar Impulse 2 departed Chongqing on Tuesday for a 1190-kilometer (642-mile) flight to the city of Nanjing in eastern China, the sixth leg of its around-the-world flight. (Photo by Chinatopix via AP Photo)

The Solar Impulse 2 plane is seen on the tarmac before taking off at Chongqing Jiangbei International Airport, to fly to Nanjing in Jiangsu province, April 21, 2015. Pilots Bertrand Piccard and Andre Borschberg are taking turns at the controls of Solar Impulse 2, which began its journey in Abu Dhabi in the United Arab Emirates on March 9, as it makes its way in the first round-the-world solar-powered flight in about 25 flight days at speeds of between 50 kph and 100 kph (30 mph to 60 mph). (Photo by Reuters/Stringer)

Swiss pilot Bertrand Piccard (top L) sits in the cockpit as staff members close the door of the Solar Impulse 2 plane before it takes off at Chongqing Jiangbei International Airport, to fly to Nanjing in Jiangsu province, April 21, 2015. (Photo by Reuters/Stringer)

Swiss pilots Bertrand Piccard (top) waves to staff from the cockpit of Solar Impulse 2 plane as they celebrate after the plane landed at Nanjing Lukou International Airport, Jiangsu province April 22, 2015. (Photo by Reuters/Stringer)

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

The Solar Impulse 2 plane (front) is seen on the tarmac next to other aircraft after landing at Nanjing Lukou International Airport, Jiangsu province April 21, 2015. (Photo by Reuters/China Daily)

Workers guide a solar-powered plane out of a hangar at Jiangbei International Airport in southwest China's Chongqing Municipality, Tuesday, April 21, 2015. (Photo by Chinatopix via AP Photo)

The Solar Impulse 2 plane is seen landing at Nanjing Lukou International Airport, Jiangsu province April 21, 2015. (Photo by Reuters/China Daily)