A cooling system configured to receive unregulated bleed air from a jet engine high pressure compressor, the cooling system comprising: a first precooler in fluid communication with the bleed air from the jet engine high pressure compressor; a cooling system compressor in fluid communication with and downstream from the first precooler; a cooling system precooler in fluid communication with and downstream from the cooling system compressor; a cooling system turbine in fluid communication with and downstream from the cooling system precooler; a discharge conduit in fluid communication with and downstream from the cooling system turbine; a bypass line in fluid communication with and downstream from the cooling system precooler, wherein the bypass line is in fluid communication with and upstream from the discharge conduit, and wherein the bypass line provides selective fluid communication between an inlet side and a discharge side of the cooling system turbine to bypass the cooling system turbine; and characterized by: a heat exchanger in fluid communication with and downstream from the first precooler, wherein the heat exchanger and the cooling system compressor are in separate flow paths from the first precooler, and wherein the discharge conduit is provided in fluid communication with and downstream from both the cooling system turbine and the heat exchanger; and a control valve in fluid communication with and downstream from the first precooler, wherein the control valve comprises a first outlet in fluid communication with and upstream from the heat exchanger, and wherein the control valve comprises a second outlet in fluid communication with and upstream from the cooling system compressor, and further wherein the control valve is configured to control fluid flow to each of the heat exchanger and the cooling system compressor, wherein the cooling system turbine has a variable area turbine nozzle, and wherein the variable area turbine nozzle is configured to control fluid flow from the cooling system turbine to the discharge conduit. a first precooler in fluid communication with the bleed air from the jet engine high pressure compressor; a cooling system compressor in fluid communication with and downstream from the first precooler; a cooling system precooler in fluid communication with and downstream from the cooling system compressor; a cooling system turbine in fluid communication with and downstream from the cooling system precooler; a discharge conduit in fluid communication with and downstream from the cooling system turbine; a bypass line in fluid communication with and downstream from the cooling system precooler, wherein the bypass line is in fluid communication with and upstream from the discharge conduit, and wherein the bypass line provides selective fluid communication between an inlet side and a discharge side of the cooling system turbine to bypass the cooling system turbine; and characterized by: a heat exchanger in fluid communication with and downstream from the first precooler, wherein the heat exchanger and the cooling system compressor are in separate flow paths from the first precooler, and wherein the discharge conduit is provided in fluid communication with and downstream from both the cooling system turbine and the heat exchanger; and a control valve in fluid communication with and downstream from the first precooler, wherein the control valve comprises a first outlet in fluid communication with and upstream from the heat exchanger, and wherein the control valve comprises a second outlet in fluid communication with and upstream from the cooling system compressor, and further wherein the control valve is configured to control fluid flow to each of the heat exchanger and the cooling system compressor, wherein the cooling system turbine has a variable area turbine nozzle, and wherein the variable area turbine nozzle is configured to control fluid flow from the cooling system turbine to the discharge conduit. a heat exchanger in fluid communication with and downstream from the first precooler, wherein the heat exchanger and the cooling system compressor are in separate flow paths from the first precooler, and wherein the discharge conduit is provided in fluid communication with and downstream from both the cooling system turbine and the heat exchanger; and a control valve in fluid communication with and downstream from the first precooler, wherein the control valve comprises a first outlet in fluid communication with and upstream from the heat exchanger, and wherein the control valve comprises a second outlet in fluid communication with and upstream from the cooling system compressor, and further wherein the control valve is configured to control fluid flow to each of the heat exchanger and the cooling system compressor, wherein the cooling system turbine has a variable area turbine nozzle, and wherein the variable area turbine nozzle is configured to control fluid flow from the cooling system turbine to the discharge conduit.