What indicates that an aircraft oxygen bottle is airworthy?

An aircraft oxygen bottle is considered airworthy primarily because it has been hydrostatically tested and stamped with the test date. This testing process is crucial as it ensures that the bottle can safely contain high-pressure oxygen without leaking or failing under pressure. The hydrostatic test specifically checks for structural integrity and verifies that the bottle meets the required safety standards. The test date is important as it indicates when the last evaluation was performed, ensuring that the bottle is within the timeframe established for maintaining airworthiness. It is essential that all oxygen bottles used in aviation are regularly inspected and tested to prevent risks associated with oxygen failures during flight.