An aircraft life support and inert gas generating system, comprising: an electrochemical cell comprising a cathode and an anode separated by a separator comprising a proton transfer medium; a cathode fluid flow path in operative fluid communication with the cathode between a cathode fluid flow path inlet and a cathode fluid flow path outlet; a cathode supply fluid flow path between an air source and the cathode fluid flow path inlet, and an inerting gas flow path in operative fluid communication with the cathode fluid flow path outlet and a protected space; an anode fluid flow path in operative fluid communication with the anode, including an anode fluid flow path outlet; an anode supply fluid flow path between a water source and the anode fluid flow path inlet, and an oxygen gas flow path in operative fluid communication with the anode fluid flow path outlet and an aircraft occupant breathing device; an electrical connection between a power source and the electrochemical cell; an oxygen storage tank and a fluid flow path from the oxygen storage tank to the aircraft occupant breathing device; a hydrogen source in fluid communication with the anode fluid flow path inlet; an electrical connection between the electrochemical cell and a power sink; and a controller configured to alternatively operate the life support system in alternate modes of operation selected from a plurality of modes including: a first mode in which water is directed to the anode fluid flow path inlet, electric power is directed from the power source to the electrochemical cell to provide a voltage difference between the anode and the cathode, and oxygen gas is directed from the anode fluid flow path outlet to the aircraft occupant breathing device, and a second mode in which hydrogen is directed from the hydrogen source to the anode fluid flow path inlet, electric power is directed from the electrochemical cell to the power sink, and oxygen gas is directed from the oxygen storage tank to the aircraft occupant breathing device. an electrochemical cell comprising a cathode and an anode separated by a separator comprising a proton transfer medium; a cathode fluid flow path in operative fluid communication with the cathode between a cathode fluid flow path inlet and a cathode fluid flow path outlet; a cathode supply fluid flow path between an air source and the cathode fluid flow path inlet, and an inerting gas flow path in operative fluid communication with the cathode fluid flow path outlet and a protected space; an anode fluid flow path in operative fluid communication with the anode, including an anode fluid flow path outlet; an anode supply fluid flow path between a water source and the anode fluid flow path inlet, and an oxygen gas flow path in operative fluid communication with the anode fluid flow path outlet and an aircraft occupant breathing device; an electrical connection between a power source and the electrochemical cell; an oxygen storage tank and a fluid flow path from the oxygen storage tank to the aircraft occupant breathing device; a hydrogen source in fluid communication with the anode fluid flow path inlet; an electrical connection between the electrochemical cell and a power sink; and a controller configured to alternatively operate the life support system in alternate modes of operation selected from a plurality of modes including: a first mode in which water is directed to the anode fluid flow path inlet, electric power is directed from the power source to the electrochemical cell to provide a voltage difference between the anode and the cathode, and oxygen gas is directed from the anode fluid flow path outlet to the aircraft occupant breathing device, and a second mode in which hydrogen is directed from the hydrogen source to the anode fluid flow path inlet, electric power is directed from the electrochemical cell to the power sink, and oxygen gas is directed from the oxygen storage tank to the aircraft occupant breathing device.