The effect of reactive sulfur removal from a Jet A-1 fuel with marginal thermal stability on surface deposition propensity is reported. The sulfur removal was achieved through adsorptive treatment of the fuel with activated carbon. The treated fuel was assessed for surface deposition propensity using a high Reynolds thermal stability test device. It was found that activated carbon has a strong adsorption capacity for the removal of reactive sulfur and Fe components from the fuel. This resulted in a substantial reduction of the surface deposition propensity of the Jet A-1 fuel. Density functional theory was used to investigate the role of reactive sulfur and Fe on thermal oxidative stability. Mechanistic pathways for intervention of this class of species with hydroperoxides are proposed.