Above what altitude must a pilot wear their oxygen mask if the other pilot leaves the duty station on a Part 135 flight?

The requirement for pilots to wear an oxygen mask when operating at high altitudes is essential for maintaining safe cabin pressure conditions and ensuring the physiological well-being of crew members. For Part 135 operations, the Federal Aviation Administration (FAA) mandates that if one pilot leaves their duty station, the remaining pilot must wear an oxygen mask at altitudes exceeding 25,000 feet. This rule is in place because at these altitudes, there is a significant risk of hypoxia due to the reduced availability of oxygen in the atmosphere.

When the altitude exceeds 25,000 feet, the cabin pressure may not be sufficient to ensure adequate oxygen levels for the remaining pilot without supplemental oxygen. Thus, the proper use of oxygen masks becomes critical to maintaining cognitive functions and situational awareness during flight operations. This regulation is particularly relevant in multi-pilot operations where one pilot's absence from the cockpit could affect the safety and management of the aircraft.

Understanding this altitude threshold helps reinforce the importance of safety protocols and regulations in aviation operations, ensuring that pilots are adequately prepared to handle varying flight conditions.