Solar Impulse 2: Biggest challenge of circumnavigation?

Two pilots are hoping to fly into the record books by circumnavigating the planet in a solar-powered plane.

Andre Borschberg and Bertrand Piccard are taking it in turns to fly the Solar Impulse 2 on its five-month journey.

The longest single leg will see one of them fly solo non-stop for five days and nights across the Pacific Ocean between Nanjing, China and Hawaii, a distance of 8,500km (5,270 miles).

BBC News looks at the conditions and challenges the pilots will face.

Video produced by Sara Barman