The density and speed of sound were measured for three samples of aviation jet fuel A and a synthetic fuel (S-8) derived from the Fischer-Tropsch process. Measurements of density and speed of sound were carried out at ambient pressure (83 kPa) with a rapid characterization instrument from 278.15 to 343.15 K. Density measurements of the compressed liquids ranged from 270 to 470 K with pressures to 30 MPa. A total of 529 experimental points are reported. 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.