A system for providing regulated flow of oxygen, including for flight crew or passengers on-board an aircraft, comprising: a first on-board oxygen supplier (110, 112) configured to supply oxygen in an initial stage; a second on-board oxygen supplier configured to generate oxygen on-board an aircraft in a subsequent stage; and a controller configured to control the first on-board oxygen supplier (110, 112) and the second on-board oxygen supplier, said system being characterized by: said first on-board oxygen supplier (110, 112) including a combination of a pressurized oxygen cylinder and a chemical oxygen generator; the second on-board oxygen supplier is a solid electrolyte oxygen separator configured to catalytically separate oxygen from a supply stream of air at a temperature of 650 °C to 750 °C by applying an electrical voltage; a pulsed oxygen delivery subsystem connected to the first on-board oxygen supplier (110, 112) by first and second feed lines (116, 118) and connected to the second on-board oxygen supplier by a third feed line and configured to receive oxygen supplied by said first on-board oxygen supplier (110, 112) and said second on-board oxygen supplier; first and second flow sensors disposed in said first and second feed lines (116, 118) connected between said first on-board oxygen supplier (110, 112) and said pulsed oxygen delivery subsystem, said first and second flow sensors being configured to measure flow rates of oxygen from said first on-board oxygen supplier (110, 112) to said pulsed oxygen delivery subsystem; and a third flow sensor disposed in said third feed line connected between said second on-board oxygen supplier and said pulsed oxygen delivery subsystem, said third flow sensor being configured to measure a flow rate of oxygen from said second on-board oxygen supplier to said pulsed oxygen delivery subsystem. a first on-board oxygen supplier (110, 112) configured to supply oxygen in an initial stage; a second on-board oxygen supplier configured to generate oxygen on-board an aircraft in a subsequent stage; and a controller configured to control the first on-board oxygen supplier (110, 112) and the second on-board oxygen supplier, said system being characterized by: said first on-board oxygen supplier (110, 112) including a combination of a pressurized oxygen cylinder and a chemical oxygen generator; the second on-board oxygen supplier is a solid electrolyte oxygen separator configured to catalytically separate oxygen from a supply stream of air at a temperature of 650 °C to 750 °C by applying an electrical voltage; a pulsed oxygen delivery subsystem connected to the first on-board oxygen supplier (110, 112) by first and second feed lines (116, 118) and connected to the second on-board oxygen supplier by a third feed line and configured to receive oxygen supplied by said first on-board oxygen supplier (110, 112) and said second on-board oxygen supplier; first and second flow sensors disposed in said first and second feed lines (116, 118) connected between said first on-board oxygen supplier (110, 112) and said pulsed oxygen delivery subsystem, said first and second flow sensors being configured to measure flow rates of oxygen from said first on-board oxygen supplier (110, 112) to said pulsed oxygen delivery subsystem; and a third flow sensor disposed in said third feed line connected between said second on-board oxygen supplier and said pulsed oxygen delivery subsystem, said third flow sensor being configured to measure a flow rate of oxygen from said second on-board oxygen supplier to said pulsed oxygen delivery subsystem. said first on-board oxygen supplier (110, 112) including a combination of a pressurized oxygen cylinder and a chemical oxygen generator; the second on-board oxygen supplier is a solid electrolyte oxygen separator configured to catalytically separate oxygen from a supply stream of air at a temperature of 650 °C to 750 °C by applying an electrical voltage; a pulsed oxygen delivery subsystem connected to the first on-board oxygen supplier (110, 112) by first and second feed lines (116, 118) and connected to the second on-board oxygen supplier by a third feed line and configured to receive oxygen supplied by said first on-board oxygen supplier (110, 112) and said second on-board oxygen supplier; first and second flow sensors disposed in said first and second feed lines (116, 118) connected between said first on-board oxygen supplier (110, 112) and said pulsed oxygen delivery subsystem, said first and second flow sensors being configured to measure flow rates of oxygen from said first on-board oxygen supplier (110, 112) to said pulsed oxygen delivery subsystem; and a third flow sensor disposed in said third feed line connected between said second on-board oxygen supplier and said pulsed oxygen delivery subsystem, said third flow sensor being configured to measure a flow rate of oxygen from said second on-board oxygen supplier to said pulsed oxygen delivery subsystem.