Fuel tank inerting systems and methods for aircraft are provided. The systems include a fuel tank, a first reactant source fluidly connected to the fuel tank, the first source arranged to receive fuel from the fuel tank, a second reactant source, a catalytic reactor arranged to receive a first reactant from the first source and a second reactant from the second source to generate an inert gas that is supplied to the fuel tank to fill a ullage space of the fuel tank, and an inert gas recycling system located downstream of the catalytic reactor and upstream of the fuel tank, wherein the inert gas recycling system is arranged to direct a portion of the inert gas to the catalytic reactor.