Rising costs and the uncertain supply of petroleum-derived aviation fuels have led to an interest in substitute fuels made from nonpetroleum sources. Synthetic isoparaffinic kerosenes (SPKs) are among the most promising alternatives. Two instruments were used to measure the density and speed of sound of two synthetic aviation fuels, one derived from natural gas and one from coal. In one instrument, measurements of density and speed of sound were carried out at ambient pressure (0.083 MPa) from (278.15 to 343.15) K The second instrument was used to make density measurements of the compressed liquids from (270 to 470) K with pressures up to 50 MPa. The density measurements are correlated within 0.1 % with a modified Tait equation, and adiabatic compressibilities are derived from the density and speed of sound data at ambient pressure. Data reported here are compared to previously reported data for another synthetic aviation fuel, S-8, as well as two petroleum-derived aviation fuels.