Definition
A small, portable oxygen cylinder worn or carried by a flight crew member to provide a short-duration emergency oxygen supply, typically used when leaving the aircraft's main oxygen system or during an emergency descent or evacuation from a high-altitude aircraft.
Plain English
A small personal oxygen bottle a crew member can grab in an emergency, giving them enough oxygen to move around the aircraft or get out of it without passing out from lack of air at high altitude.
Context Anchor
Seen in high-altitude flying, parachute-equipped aircraft, military aircraft, test flying, and emergency equipment discussions.
Derivation
Bail out' means to jump from an aircraft, usually with a parachute, in an emergency. The 'bottle' is simply the small oxygen cylinder. Together the term describes the oxygen supply a crew member uses while bailing out of, or moving around inside, an aircraft at altitudes where the air is too thin to breathe.
Why Pilots Care
Provides critical oxygen supply that prevents hypoxia during high-altitude ejections, directly affecting pilot survival.
Grounding Statement
If a pilot has to leave the aircraft above breathable air, the bail-out bottle is the temporary oxygen source for the trip down.
Intuition Check
“Bail-out” here does not mean a rescue or financial help. It means leaving the aircraft in an emergency, and the bottle supplies oxygen after that.
Example Sentence 1
Before disconnecting from the main oxygen system, the crew member switched over to the bail-out bottle clipped to their harness.
Example Sentence 2
During the emergency, she activated the bail-out bottle immediately after clearing the cockpit.