What is the oxygen requirement for crew and passengers in an unpressurized aircraft at 15,000 feet?

In unpressurized aircraft, the requirement for supplemental oxygen is dictated by regulations that are in place to ensure the safety and well-being of both crew and passengers at high altitudes. At 15,000 feet, the atmospheric pressure decreases, resulting in reduced levels of oxygen available for breathing.

The correct answer identifies the specific altitude requirements for oxygen use. The regulation states that flight crew members are required to use supplemental oxygen at altitudes above 14,000 feet, while passengers must begin to use oxygen at 15,000 feet. This graduated requirement is based on physiological factors, as the mixture of oxygen in the air becomes thinner as altitude increases, which can lead to hypoxia—a condition caused by insufficient oxygen.

This understanding of oxygen requirements is crucial not only for compliance with safety regulations but also for ensuring that all occupants remain alert and capable of responding to in-flight situations in high-altitude operations. Thus, the correct answer emphasizes the importance of recognizing these altitude thresholds for the use of supplemental oxygen for safe operations in unpressurized aircraft.