A rapid compression machine is used to study the autoignition characteristics of surrogate jet fuels with unique physical and/or chemical characteristics that may have an impact on the combustion properties. These surrogate fuels were specifically designed to study of the influence of chemical composition on autoignition, including the influence of branching in isoparaffins and effects of aromatic structures. The tests were conducted via a rapid compression machine that employed the direct test chamber charge preparation method which allows for high reproducibility of measurements. Ignition delay measurements are compared between the conventional military jet fuel and neat surrogate jet fuels. Measurements were made at a compressed pressure of 20 bar at equivalence ratios of 1.0, 0.5, and 0.25 in the low temperature region (625 K and 735 K). The results show significant variability in the ignition properties at these low temperature conditions based on the chemical structure. This variability may require attention when the engine is running outside the normal operational map or for new engine architectures in the future.