$1.65M NASA-funded Green Flight Challenge is a flight competition for quiet, practical, Green aircraft that will take place at the CAFE Foundation Flight Test Center at Charles M. Schulz Sonoma County Airport in Santa Rosa, California. It is the largest-ever prize for civil aviation and there are currently 13 teams entered. Team aircraft must fly 200 miles in less than two hours using the energy equivalent of less than 1 gallon of gasoline per occupant. Team aircraft include those propelled by gasoline, bio-diesel, hydrogen, and electricity.
For comparison, a large airliner, A380 or 747, will do around 3.5 litres per passenger per 100km. This is about 56 passenger miles per US Gallon, or 67 to an Imperial Gallon.
http://cafefoundation.org/