What is the minimum altitude at which supplemental oxygen must be used for flight times exceeding 30 minutes?

The correct altitude where supplemental oxygen becomes necessary for flights lasting longer than 30 minutes is 12,500 feet MSL. At this altitude, the partial pressure of oxygen in the atmosphere decreases sufficiently that, for many individuals, acute physiological effects like hypoxia can begin to occur. The Federal Aviation Administration (FAA) regulations specify that pilots must use supplemental oxygen in this scenario in order to maintain their ability to perform safely and effectively.

It’s important to note that while supplemental oxygen is recommended at this altitude, the requirement becomes mandatory at higher altitudes. Specifically, when flying above 14,000 feet MSL, crew members must use oxygen continuously, and above 18,000 feet MSL, all occupants in the aircraft must utilize supplemental oxygen. These regulations are in place to ensure safety by minimizing the risks associated with reduced oxygen availability at high altitudes.