An air inert gas generating system consists of heat exchangers, a heating element, and a plurality of solid oxide electrochemical gas separator (SOEGS) cells. The SOEGS cells are interconnected in series to create a stack. A voltage is applied to the stack causing oxygen ions to be transported from the air flowing through the cathode through the electrolyte to the anode side of the SOEGS, resulting in oxygen-depleted gas. The oxygen-depleted gas can be used to inert the ullage of aircraft fuel tank or support the fire suppression system in the cargo hold. The oxygen-enriched gas can be used for other purposes.