Abstract: The present air conditioning system bleeds high pressure, hot, compressed air from the compressor section of a gas turbine engine and passes the high pressure flow of air directly through a single heat exchanger, through a flow control valve, is used to drive a supersonic turbine device, exits the supersonic turbine device as a low pressure, cooled flow of air and passes through a water separator prior to being used to cool the cabin zone. The primary advantages of the improved air conditioning system includes the elimination of the necessity for pressure regulation and only one heat exchanger is required. Furthermore, the improved air conditioning system is modulely designed and allows for a more flexibility, enabling the components to be more selectively located. Furthermore, the system is considerably smaller and lighter in weight.