For five days and nights, André Borschberg and his solar aircraft will battle exhaustion, discomfort and technological limitations as they cross the lonely 5,000 miles of ocean that swallowed Amelia Earhart 78 years ago.

Since beginning their circumnavigation of the world in Abu Dhabi in March, Borschberg and his flight partner Bertrand Piccard have been piloting the single-seater Solar Impulse II on alternating legs of up to 20 hour, breaking records for solar flight as they go. But Borschberg’s flight from Nanjing in China to the islands of Hawaii will dwarf all their previous feats, and smash the previous endurance record for solo flight in any plane by around two days.
...
During the day, the pilots will climb to an altitude of 9,000m. But as the sun disappears, they will power down the propellors and glide. Using the motors sparingly the plane will drop to 1,000m – below the clouds. As day breaks, they will have just 5-10% battery capacity and will have to find a clear patch of sky or risk plunging into the ocean.
...
Piloting the plane into clear skies will require constant attention, meaning the pilots will snatch sleep in 20-minute naps. Both will practice meditation and yoga (adapted to the cramped cockpit) in order to cope with the mental adversity. Borschberg said the external adventure would be mirrored by his own “personal exploration”.

http://www.theguardian.com/environment/2015/may/25/solar-aircraft-impulse-2-flown-pacific-world-record-bid