A method for reducing outside air inflow required for aircraft passenger cabin air quality is provided. The method determines when passenger cabin air quality is the driving outside air inflow requirement and reduces the outside air inflow to that required for passenger cabin air quality. In one embodiment, there is provided a method for reducing outside air inflow required for aircraft passenger cabin air quality using a fixed minimum outflow valve open area setpoint. In another embodiment, there is provided a method for reducing outside air inflow required for aircraft passenger cabin air quality using calculations that are repeated at regular intervals and using a mathematical function relating an outside air inflow requirement to a set of independent variables. In another embodiment, there is provided a method for calculating an aircraft fuselage leakage value and communicating the fuselage leakage value and an increase in a fuel consumption rate due to an additional amount of outside air inflow required to replenish air loss due to fuselage leakage, due to aerodynamic drag, and due to reduced thrust recovery.