What indicates that an aircraft oxygen bottle is airworthy?

The indication that an aircraft oxygen bottle is airworthy is that it has been hydrostatically tested and stamped with the test date. This hydrostatic testing is essential for determining the integrity and strength of the oxygen bottle. During this process, the bottle is filled with a liquid and pressurized to verify that it can withstand the required pressures without leaking or deforming.

The test date stamp serves as a record to ensure that the bottle is maintained within its safe operational limits and that it has been inspected and deemed structurally sound within a certain time frame. Regular hydrostatic testing is critical for safety in aviation, ensuring that the oxygen system remains reliable for emergency use. This safety measure is mandated by aviation regulations to avoid potential failures of oxygen systems during flight, thereby ensuring passenger and crew safety.

The other factors, while they may provide some level of assurance regarding the oxygen bottle's condition, such as a green label or a manufacturer's warranty, do not directly confirm its operational readiness or compliance with safety standards like the hydrostatic test does.