At some point in the future, the transportation system will have to start to use non-petroleum fuels. With the long lead times for the development of a new aircraft, it is important to consider the use of alternate fuels now. This paper covers a comparison of alternate fuels for aviation gas turbines in both subsonic and supersonic aircraft. It also addresses the economic comparison between upgrading future synthetic fuels to meet current hydrogen levels and modifying the jet engine to accept a fuel with a lower hydrogen content.
