The current incentive for safety fuels is due to excessive loss of aircraft in Vietnam due to fires. Evaluation of four classes of thickened fuels eliminates “canned-heat” gels, the visco-elastic Napalm type, and the polymer-thickened fluids. Emulsions-thickened fuels seem more compatible with aircraft systems. Points of superiority include ease of removal from tanks, good atomizing properties in engines, and constancy of rheological properties over a wide temperature range.Recent work on an Army-sponsored contract to develop emulsion safety fuels for Army helicopters and cargo planes has uncovered a number of formulations containing at least 97% fuel. Based on early laboratory data, these emulsions appear to have good stability at −30 to 130 F. The separation of JP-4 varies from 1-10% after several cycles of heating and cooling between these limits.One nonaqueous emulsion, WS-X-7063, has provided valuable background information. The yield stress of the emulsion can be varied 1000-3500 dynes/ cm2 by varying the ratio of continuous phase to emulsifier. Its performance charateristics in various engine fuel systems are under investigation. We hope the information produced will enable us to develop a fuel acceptable for use in selected military applications.