Abstract: The invention relates to an air conditioning system for an aircraft cabin, comprising two motorized turbomachines (16a, 16b) each comprising a compressor (14a, 14b) supplying an outlet (24) common to the compressors and a turbine, one of the turbines, referred to as water extraction turbine (16a), being dedicated to a water extraction loop (28) and the other turbine, called cooling turbine (16b), helping cool the air. The air conditioning system comprises a network of pipes and associated valves, connected to the common outlet (24) of the compressors and making it possible to supply, from the common outlet of the compressors: either the inlet (160) of the water extraction turbine (16a), or the inlet (164) of the cooling turbine (16b), bypassing the turbine (16a) and the water extraction loop, or an outlet (60) of the air conditioning system directly, bypassing the cooling turbine (16b) and the water extraction turbine (16a).