14 CFR 91.211 — Supplemental Oxygen
Crew must use supplemental oxygen above 12,500 ft for over 30 minutes, above 14,000 ft at all times. Passengers must be provided oxygen above 15,000 ft.
Regulation Text
No person may operate a civil aircraft of U.S. registry at cabin pressure altitudes above 12,500 feet MSL up to and including 14,000 feet MSL unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration. Above 14,000 feet MSL, the required minimum flight crew must use supplemental oxygen during the entire flight at those altitudes. Above 15,000 feet MSL, each occupant must be provided with supplemental oxygen.
Note: This is an excerpt. Refer to the full regulation in eCFR for the complete text.
Plain-English Explanation
Oxygen rules by altitude: 12,500-14,000 feet — crew must use oxygen after 30 minutes at these altitudes. Above 14,000 feet — crew must use oxygen the entire time. Above 15,000 feet — oxygen must be available for all passengers too. These rules exist because hypoxia (oxygen deprivation) impairs judgment and motor skills, often without the pilot realizing it. At 15,000 feet, time of useful consciousness is about 15-30 minutes.
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Related Regulations
14 CFR 91.135 — Operations in Class A Airspace
All operations in Class A airspace (18,000 MSL to FL600) must be conducted under IFR with an ATC clearance.
§91.11914 CFR 91.119 — Minimum Safe Altitudes
1,000 feet above obstacles in congested areas (within 2,000 ft horizontal), 500 feet AGL over uncongested areas, and safe altitude over open water or sparsely populated areas.
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