A cooling system for cooling heat loads on board an aircraft comprises a cold producing device, a first cold carrier fluid circuit, which is thermally coupled to the cold producing device and is connected to a first heat load in order to carry off heat from the first heat load, and a second cold carrier fluid circuit, which is connected to a second heat load in order to carry off heat from the second heat load. A coupling system of the cooling system is adapted 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. In a method for operating such a cooling system for cooling heat loads on board an aircraft, the first cold carrier fluid circuit is selectively thermally coupled to the second cold carrier fluid circuit or thermally uncoupled from the second cold carrier fluid circuit by means of the coupling system.