Plain English Meaning
The bottled or stored oxygen on board the aircraft, along with the hoses, regulators, and masks needed to breathe it when the air outside is too thin.
Full Definition
The aircraft system or portable equipment that stores and delivers breathable oxygen to pilots, crew, and passengers when ambient air at altitude no longer contains enough oxygen to maintain normal physiological function. An oxygen supply typically consists of a storage source (compressed gas cylinders, liquid oxygen, or chemical generators), pressure regulators, delivery lines, and masks or cannulas used by the occupants.
Context Anchor
Used in preflight planning and checks for flights where may be needed or required.