Abstract: The disclosure provides apparatus and methods of use pertaining to providing concentrated oxygen to an oxygen-dependent airline passenger. One embodiment provides an on-board oxygen concentrator that includes at least one air compressor secured in a compartment of an aircraft and at least one zeolite sieve bed also secured in a compartment of the aircraft, such as the same compartment. The zeolite sieve beds are operatively connected to the compressor to receive compressed aircraft cabin air from the compressor and emit concentrated oxygen. A pressure regulator controls pressure of oxygen emitted to a passenger of the aircraft. Other embodiments are also disclosed.