In July, Solar Impulse 2 became the first airplane to fly around the world without using fuel. At the same time, the U.S. National Aeronautics and Space Administration has been working on electric planes. These developments mean air travel and transport could become more environmentally friendly, with less pollution and fewer greenhouse gas emissions, and planes would be quieter.

In July, Solar Impulse 2 became the first airplane to fly around the world without…