Above what altitude MSL must a pilot of an unpressurized aircraft use supplemental oxygen?

The use of supplemental oxygen is a crucial safety measure in aviation, particularly for unpressurized aircraft flying at higher altitudes. According to regulations, pilots must use supplemental oxygen when operating above 14,000 feet Mean Sea Level (MSL) because at this altitude, the partial pressure of oxygen decreases significantly. This reduction can lead to hypoxia, a condition where the body is deprived of adequate oxygen, impairing cognitive and physical functions.

By implementing supplemental oxygen above 14,000 feet, pilots can maintain their performance and ensure safety for themselves and their passengers. Understanding the physiological effects of altitude is essential for all aviators, and knowing when to use supplemental oxygen is a key part of those safety protocols.