The invention relates to a device (10) for heating an aircraft cabin and comprises a first hot air supply line (12) that leads to an air conditioning unit (14), a flow control valve (16) that is disposed in the first hot air supply line (12) upstream from the air conditioning unit (14), and a second hot air supply line (18) that branches off from the first hot air supply line (12) between the flow control valve (16) and the air conditioning unit (14) and bypasses the air conditioning unit (14). In order to assure air conditioning of the aircraft cabin in the event of a failure of the air conditioning unit (14) a third hot air supply line (20) branches off from the first hot air supply line (12) upstream from the flow control valve (16), which third hot air supply line (20) connects the first hot air supply line (12) to the second hot air supply line (18). Further a first close off mechanism is disposed in the second hot air supply line (18) upstream from the junction with the third hot air supply line (20), which first close off mechanism in its closed position prevents a flow from the second hot air supply line (18) back into the first hot air supply line (12). Finally a second close off mechanism is disposed in the third hot air supply line (20) upstream from the junction with the second hot air supply line (18).