Solar Impulse completed the first manned intercontinental flight using only solar energy in 2012.
The Swiss Solar Impulse project used a large, lightweight aircraft covered with photovoltaic cells. In 2012, the aircraft flew from Switzerland to Morocco and back, demonstrating that solar electricity could power a piloted aircraft over long distances. The flight was a technological demonstration rather than commercial air transport.
Solar Impulse 1 carried lithium-polymer batteries so it could continue flying after sunset. During daylight, its solar cells powered the motors and recharged the batteries. The aircraft’s extremely light structure, low speed, and large wingspan were essential to keeping energy demand low.
The later Solar Impulse 2 completed a round-the-world journey in 2016. That achievement is separate from the 2012 intercontinental flight. Solar Impulse aircraft were not designed to carry many passengers; their purpose was to test clean-energy aviation and advanced lightweight materials.