Last month, Solar Impulse II achieved something that no other airplane had ever done before. It flew around the world without using a drop of fuel, powered only by the sun. In the roughly 25,000 miles that it flew, Solar Impulse made two record-breaking ocean crossings, and traversed Europe, Asia, and North America. The two pilots, Bertrand Piccard and André Borschberg, endured temperatures in the cockpit that swung between -40 and 104 degrees Fahrenheit.

Since Piccard and Borschberg's first solar powered flight across the United States in 2013, they've developed seemingly unlikely partnerships with corporations eager to participate in an environmental dream, built a prototype solar plane that functions as a flying laboratory, and nurtured the idea that being environmentally friendly doesn't have to be depressing or expensive.