Abstract: An oxygen supply system for an aircraft includes a control valve, a reservoir bag, a respiration device and a sensor device, wherein the control valve is designed in such a way that oxygen can be supplied to the reservoir bag until a predetermined quantity of oxygen is adjusted in the reservoir bag. The respiration device may be designed in such a way that breathing gas can be provided for a passenger. The sensor device may be designed in such a way that an exhalation is detectable. The reservoir bag may be designed in such a way that a predetermined quantity of oxygen can be metered into the reservoir bag during the exhalation. The reservoir bag may be designed in such a way that breathing gas can be supplied to the respiration device in a pulse-like fashion. The oxygen supply system may include a first and a second operation mode.