A confluence of environmental and supply security are driving the aviation community to consider alternatives to petroleum-derived jet fuels.  It was recognized early on in the process that the sheer size of the existing aircraft fleet and supporting jet fuel infrastructure, along with regulatory constraints, precluded the introduction of a chemical energy carrier requiring aircraft or fuel handling equipment modifications.  Consequently, the chosen path forward was focused on synthetic alternatives with essentially identical chemical compositions and physical properties, called drop-in fuels.  This chapter will describe the regulatory basis enabling the use of these fuels by the existing aircraft fleet and the technical approach used to validate the drop-in nature of these fuels.

A confluence of environmental and supply security are driving the aviation community to consider alternatives to petroleum-derived jet fuels.  It was recognized early on in the process that the sheer size of the existing aircraft fleet and supporting jet fuel infrastructure, along with regulatory constraints, precluded the introduction of a chemical energy carrier requiring aircraft or fuel handling equipment modifications.  Consequently, the chosen path forward was focused on synthetic alternatives with essentially identical chemical compositions and physical properties, called drop-in fuels.  This chapter will describe the regulatory basis enabling the use of these fuels by the existing aircraft fleet and the technical approach used to validate the drop-in nature of these fuels.