What does "O-na" mean in the context of aircraft safety equipment?

In the context of aircraft safety equipment, "O-na" signifies that there is no specific safety equipment available for that item or situation. This notation helps to clarify what equipment is present and what is not, ensuring that crew members and emergency responders are aware that certain safety measures or gear are not provided. By marking something as "O-na," it indicates an absence rather than a temporary unavailability, which is crucial for safety assessments and emergency preparedness.

The other answers imply varying states of availability or applicability of safety equipment, but they do not accurately convey the meaning of "O-na." Understanding this distinction is vital in the field of aircraft safety, as it directly impacts readiness and response during emergencies.