The invention relates to a device and a method for distributing air in a cargo aircraft. The cargo aircraft has an air distribution system (10) which is connected to at least one cargo deck. The air distribution system comprises a source (12, 14, 16, 18) for bleed air, at least one so-called air conditioning unit (28, 38) for treating the bleed air, a mixing unit (32) which receives treated bleed air from the air conditioning unit (28, 38) and delivers it to the at least one cargo deck, and at least one shut-off valve (58, 60, 62, 64) between the mixing unit (32) and the cargo deck in order to interrupt or completely release the air supply to the cargo deck. In order to reduce the bleed air requirement, a cockpit switch (82, 84, 86, 88) co-operating with the shutoff valve is provided, the operation of which switch causes the at least one shutoff valve (58, 60, 62, 64) to take up an intermediate position. For this purpose the shutoff valve (58, 60, 62, 64) is formed as a motor-operated control valve which can take up any desired intermediate position between its completely open and completely closed position. A control unit (92) establishes for each possible operating state of the air distribution system a desired air volume balance and adjusts the flow volume through the at least one air conditioning unit (28, 38) in accordance with the desired air volume balance established for the respective operating state such that the pressure in the mixing unit (32) is at a constant, predetermined value.