How Solar Impulse 2 became the first aircraft to complete a 40,000 km fuel-free journey around the world

Solar Impulse 2 completed the first fuel-free flight around the world, traveling approximately 40,000 kilometers using only solar energy.

The aircraft relied on more than 17,000 solar cells in its wings to collect energy, with surplus stored in onboard batteries for night flight.

The mission, which began in Abu Dhabi on March 9, 2015, and returned in July 2016, involved 16 stopovers over 16 months.

Solar Impulse 2's wingspan exceeded that of a Boeing 747, but it used lightweight materials and electric motors to demonstrate renewable energy in aviation.