Solar Impulse 2 landed in Egypt's capital, Cairo on Wednesday, July 13 after a 51-hour flight from Spain in a penultimate flight.

The adventure is to encourage people to promote clean and renewable energies.

Solar Impulse 2 has a wingspan of 72 meters, 12 meters longer than that of Boeing 747, but weighs only 2.3 tonne.  Equipped with 17,248 solar cells, the zero-fuel plane runs on stored energy at night.