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Over the next few days, three teams are competing to win $1.65 million in prize money at the Green Flight Challenge in Santa Rosa, California. The event is hosted by NASA, run by the Comparative Aircraft Flight Efficiency Foundation, and sponsored by Google. In order to win, a plane will need to fly 200 miles in less than two hours and use less than one gallon of gasoline per occupant or the equivalent in electricity. Ar travel is responsible for a large and growing percent of greenhouse gas emissions worldwide.

Image: NASA/Flickr.