A fuel oxygen reduction unit is provided for reducing an oxygen content of a flow of liquid fuel to an engine. The fuel oxygen reduction unit includes: a stripping gas supply line for providing a flow of stripping gas; a contactor defining a liquid fuel inlet, a stripping gas inlet and a fuel/gas mixture outlet, the stripping gas supply line in airflow communication with the stripping gas inlet; a means for modulating the flow of stripping gas through the stripping gas supply line; and a controller operable with the means for modulating the flow of stripping gas through the stripping gas supply line to modulate the flow of stripping gas through the stripping gas supply line in response to an engine operability parameter.