The US Air Force is currently certifying ALL of their aircarft to run a 50/50 blend of Jet A and synthetic kerosene derived from natural gas and coal. Their goal is to eliminate reliance on foriegn oil. A number of airplanes have been tested, including supersonic fighters and bombers. This is not an experiment, they are doing it now with the intent of changing over in the next couple of years.

Bio-fuel is more desireable for airlines because it offers reduced emissions. Also, with the right feedstock, it does not have to compete with food agriculture. That's why they are interested in jatropha...it's non-edible and can be cultivated in areas where no food will grow anyway.