The invention relates to highly reactive fuel compositions primarily intended for supersonic combustion ramjet engines. In particular, the invention provides highly reactive fuel compositions capable of efficient oxidation and thrust production even within the low combustor residence time of a supersonic combustion ramjet engine. The fuel compositions comprise specific blends of a major fuel component and an additive which, on pyrophoric combustion thereof, produces sufficient heat energy to spontaneously ignite and burn the major fuel component at a substantially increased rate.