Imagine a '57 Chevy cruising through the air, and you get an idea of what single-engine, propeller-driven airplanes do to the environment. The average private plane, such as the popular two-seat Cessna 172, is 30 years old. It carries a four-cylinder piston engine designed in the 1940s that burns leaded gasoline, has no catalytic converter, and gets as little as 12 miles per gallon. “It’s fair to say that small aircraft are gross polluters,” says Mark Moore, an engineer who has led personal-aircraft projects for NASA.

This month, on an airstrip just north of San Francisco, a handful of inventive pilots hope to help turn that sooty reputation around, as they compete in the nation’s first eco-aviation challenge, called the Green Prize. Up to 16 teams will fly their experimental personal air vehicles (PAVs), each tuned for optimal fuel efficiency, along a course that sweeps above Northern California and includes climbs and descents. The team that burns the least fuel over the two-hour race—30 mpg is the record for a two-seat PAV—wins up to $50,000.

But the organization behind the race, the Comparative Aircraft Flight Efficiency Foundation (or CAFE, pronounced “café”), has a much grander goal in mind. Inspired by the $10-million Automotive X Prize competition for a 100mpg car, CAFE president Brien Seeley is courting private contributors who can fund a prize of up to $10 million for the first plane to fly 100 miles, at 100 miles per hour, on one gallon of gasoline. (Though he has yet to write a check, Google co-founder Larry Page attends all the CAFE meetings.)

Only about 170,000 personal planes are registered to fly in the U.S., a pittance compared with the nation’s 244 million cars. But Seeley believes that personal aviation can free us from gridlock. “It’s time to get off the pavement,” he says. “The goal of the Green Prize is to bring forth a consumer-popular vehicle that transforms the way we move”—trading traffic jams for what he calls “the wormhole in the sky.”
Seeley and Moore, the co-creators of the Green Prize, envision a future in which people own or rent inexpensive PAVs, user-friendly planes for quick hops of 50 to 500 miles from one neighborhood airstrip to the next. To help make that happen, NASA is funding a five-year “Centennial Challenge” program of annual CAFE-run competitions, including the Green Prize, to encourage PAV technology. Last year’s inaugural competition featured awards for handling, noise reduction and overall performance.