A supercharging system (11) for a gas turbine system (13) is provided the supercharging system having a fan (41) mechanically coupled to the turbine shaft (27) of the turbine system. A bypass subsystem (59) is provided or optionally conveying a portion of the airstream output to other uses. The supercharging system may also be used in conjunction with a combined cycle power system and a bypass subsystem optionally conveys a portion of the airstream output to a heat recovery steam generator (15).