FAR 91.211 — Supplemental Oxygen

This regulation governs when supplemental oxygen must be used by flight crew and passengers. At cabin pressure altitudes above 12,500 feet MSL up to and including 14,000 feet MSL, the required minimum flight crew must use supplemental oxygen for any portion of flight at those altitudes that is more than 30 minutes in duration. Above 14,000 feet MSL, the flight crew must use oxygen at all times. Above 15,000 feet MSL, each occupant (including passengers) must be provided supplemental oxygen. Understanding these thresholds is essential for high-altitude cross-country planning and mountain flying.