A catalytic inerting system (CIS) architecture includes a fuel tank including a fuel tank inlet and a fuel tank outlet, the fuel tank defining a space for containing a liquid fuel and an ullage space above the liquid fuel containing an ullage gas. A catalytic reactor is in fluid communication with the fuel tank, the catalytic reactor having a catalytic inlet and a catalytic outlet, wherein the catalytic reactor receives an ullage gas flow from the fuel tank outlet and performs a catalytic reaction on the ullage gas to produce a more inert flow from the catalytic outlet to the fuel tank inlet. A bypass line provides a flow pathway between the fuel tank inlet and the fuel tank outlet, thereby bypassing the fuel tank, and a flow control mechanism controls relative flows of the inert flow from the catalytic outlet to the fuel tank inlet versus through the bypass line.