•Without any design change, drop-in sustainable aviation fuel (SAF100) can be tailored to promote energy savings of at most 0.33 %. Such fuel would have an energy density of 34.3 GJ/m3 which is just inside the ± 2σ experience interval of conventional jet fuel; 34.0–35.6 GL/m3.•By eliminating the minimum aromatics content imposed on SAF100, optimized fuel could afford at most 0.40% energy savings for a fuel with an energy density of 34.2 GJ/m3, or 0.33% energy savings for a fuel with an energy density of 35.7 GJ/m3.•By raising the minimum energy density requirement (or design point reference fuel) by 4% and increasing the lower heating value of the design point reference fuel by 1%, both of which are attainable for optimized, 100% SAF without aromatics (Jet-X), supersonic aircraft can be made at most 2.3% more energy efficient.•The composition and property characteristics of optimized SAF100 and Jet-X are discussed at length in this article. Whether the feedstock for sustainable aviation fuel (SAF) originates from agriculture or from waste streams, life cycle CO2 emissions per unit enthalpy are lower for SAF than they are for petroleum distillates primarily because of differences on the front end such as fostered growth of crops or decreased demand for resources or acreage to manage wastes. This work, however, is concerned with what happens on the consumption side. Sustainable aviation fuel is required by ASTM D4054 / D7566 to meet a higher thermal stability standard than petroleum distillate fuels and this characteristic can be leveraged to improve energy efficiency in new engine or aircraft designs where a commitment has been made to burning fuel that meets a specification beyond that of conventional JetA. Beyond thermal stability, non-drop-in SAF (Jet-X) developers have the opportunity to further increase the value of their product by infusing higher-than-conventional-JetA energy density (enthalpy per unit volume, ED) into their SAF. Finally, fuel specific energy (enthalpy per unit mass, LHV) has a direct impact on aircraft efficiency which we have determined to be 0.43% per MJ/kg increase in LHV depending on the mission and aircraft model, and this is applicable to both drop-in and non-drop-in applications. While higher energy density fuels may be leveraged in a new aircraft design to decrease drag and weight, aircraft development potential with reduced tank volumes is typically constrained by other factors such as wing packaging, passenger volume requirements and overall center of gravity and flight control law restrictions.