What is required for crew members in unpressurized aircraft above 15,000 feet?

For unpressurized aircraft operating at altitudes above 15,000 feet, the regulations stipulate that supplemental oxygen is required for all occupants. This is crucial for safety, as the partial pressure of oxygen decreases as altitude increases, potentially leading to hypoxia (insufficient oxygen supply to the body).

At altitudes above 15,000 feet, the risk of experiencing hypoxia increases significantly, and to mitigate these risks, regulations mandate that all individuals aboard use supplemental oxygen. This ensures that everyone has adequate oxygen, helping to maintain the overall safety and well-being of the crew and passengers during flight.

In contrast, using supplemental oxygen only for the required minimum crew would not provide necessary protection to all individuals onboard, and the suggestion that no oxygen is required for IFR flights fails to recognize that even under instrument flight rules, the risks at higher altitudes still apply. Thus, the requirement for all occupants to have access to supplemental oxygen at these altitudes is aimed at safeguarding against oxygen deprivation and ensuring a safer flight environment.