Liquid hydrocarbon fuels are complex hydrocarbon mixtures, made even more complex when oxidation reactions produce a variety of oxygenated species. Heart-cut multidimensional gas chromatography coupled with chemical ionization mass spectrometry was applied to the quantification of alkyldihydrofuranones in several fossil and alternatively derived jet fuels. The fuels were then subjected to thermal oxidative stress for extended times using a purpose-designed experimental system. The concentration of furanones in all fuels increased over the course of the experiment, to a maximum of 7.5 mg/L in a hydrotreated fuel. The analytical method is robust with R-2 for all analytes above 0.9993 and relative standard deviation below 6%. A mechanism for the formation of these compounds via intramolecular cyclization is also postulated.