The Green Flight Challenge is part of NASA's Centennial Challenges designed to stimulate innovation and competition in solar system exploration and other ongoing NASA mission areas, the agency said.

NASA has in the past supported a Centennial Challenge around Personal Air Vehicles (PAVs) which are small, relatively inexpensive aircraft that can be used for personal travel -- basically a car in the sky.

NASA aeronautics developed the PAV concept with the idea of transporting people to within just a few miles of their doorstep destination at trip speeds three to four times faster than airlines or cars. NASA predicts that up to 45% of all miles traveled in the future may be in PAVs. This will relieve congestion at metropolitan hub airports and the freeways that surround them, reduce the need to build new highways and save much of the 6.8 billion gallons of fuel wasted in surface gridlock each year, NASA said.