An aircraft cooling system for cooling heat loads on board an aircraft includes a cold producing device, a first cold carrier fluid circuit thermally coupled to the cold producing device and connected to a first heat load in order to carry off heat from the first heat load, a second cold carrier fluid circuit connected to a second heat load in order to carry off heat from the second heat load, a heat exchanger disposed in the second cold carrier fluid circuit and configured to thermally couple the second cold carrier fluid circuit to an ambient temperature surrounding the aircraft, and a coupling system configured to selectively thermally couple the first cold carrier fluid circuit to the second cold carrier fluid circuit or thermally uncouple it from the second cold carrier fluid circuit.