Swiss pilot Bertrand Piccard was behind the controls of Solar Impulse 2, which can fly for days on only energy from the sun.
"It's a project for energy, for a better world," Piccard told journalists before taking off.
Pilots Piccard and Swiss entrepreneur Andre Borschberg have taken turns flying the plane on its 22,000-mile (35,000-kilometre) trip around the world.
Borschberg piloted the flight's Pacific stage, a 4,000-mile flight between Nagoya, Japan, and Hawaii.
Solar Impulse 2 arrived in Cairo after a two-day flight from Spain, finishing the 3,745 kilometre journey with an average speed of 76.7 kilometres an hour.
The single-seat aircraft, no heavier than a car but with the wingspan of a Boeing 747, is clad in 17,000 solar cells. During night-time flights it runs on battery-stored power.
It typically travels at a mere 30 miles (48 kilometres) per hour, although its flight speed can double when exposed to full sunlight.