Supplemental oxygen requirements14 CFR 91.211 Supplemental oxygen
At cabin pressure altitudes above 12,500 feet MSL up to and including 14,000 feet, the required minimum flight crew must use supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration; above 14,000 feet they must use it the entire time, and above 15,000 feet every occupant must be provided with oxygen.
By the ATIS Alerts team · Updated October 15, 2026 · Regulation text current as of October 14, 2026. A study aid based on the official regulation text, not legal advice or an FAA interpretation.
At a glance
- Above 12,500 up to and including 14,000 feet MSL: the required minimum flight crew uses oxygen for the part of the flight at those altitudes of more than 30 minutes (a)(1).
- Above 14,000 feet MSL: the required minimum flight crew uses oxygen during the entire flight time at those altitudes (a)(2).
- Above 15,000 feet MSL: each occupant must be provided with oxygen (a)(3).
- All of these are cabin pressure altitudes, not the altitude the aircraft is flying (a).
- Pressurized aircraft above FL 250 need at least a 10-minute supply for each occupant in case of a pressurization loss (b)(1)(i).
In plain English
Section 91.211 sets oxygen rules for civil aircraft of U.S. registry in three steps, all measured as cabin pressure altitude in feet MSL. Above 12,500 feet up to and including 14,000 feet, the required minimum flight crew must be provided with and use supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration. Above 14,000 feet, the required minimum flight crew must be provided with and use oxygen during the entire flight time at those altitudes.
The third step is about passengers. Above 15,000 feet cabin pressure altitude, each occupant of the aircraft must be provided with supplemental oxygen. The rule says provided with, not uses, for occupants, while the crew rules in (a)(1) and (a)(2) say provided with and uses.
Paragraph (a) is measured by cabin pressure altitude, not by the altitude the aircraft is flying. Paragraph (b) adds rules for pressurized cabins: above flight level 250, at least a 10-minute supply for each occupant in addition to any oxygen needed under (a), for use if a descent is needed after a loss of pressurization. Above flight level 350, one pilot at the controls must wear and use a secured and sealed mask, with an exception at or below flight level 410 when two pilots at the controls each have a quick-donning mask that can be placed on the face with one hand from the ready position within 5 seconds.
Common mistakes
- Using 12,500 feet as the point where passengers need oxygen. Occupants must be provided with oxygen above 15,000 feet (a)(3).
- Treating the 30-minute allowance as applying above 14,000 feet. Above 14,000 feet the crew uses oxygen the entire time (a)(2).
- Measuring by indicated altitude in a pressurized airplane. The paragraph (a) limits are cabin pressure altitudes.
The official text
14 CFR 91.211 as published on the eCFR, current as of October 14, 2026.
(a) General. No person may operate a civil aircraft of U.S. registry—
(1) 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;
(2) At cabin pressure altitudes above 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen during the entire flight time at those altitudes; and
(3) At cabin pressure altitudes above 15,000 feet (MSL) unless each occupant of the aircraft is provided with supplemental oxygen.
(b) Pressurized cabin aircraft. (1) No person may operate a civil aircraft of U.S. registry with a pressurized cabin—
(i) At flight altitudes above flight level 250 unless at least a 10-minute supply of supplemental oxygen, in addition to any oxygen required to satisfy paragraph (a) of this section, is available for each occupant of the aircraft for use in the event that a descent is necessitated by loss of cabin pressurization; and
(ii) At flight altitudes above flight level 350 unless one pilot at the controls of the airplane is wearing and using an oxygen mask that is secured and sealed and that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude of the airplane exceeds 14,000 feet (MSL), except that the one pilot need not wear and use an oxygen mask while at or below flight level 410 if there are two pilots at the controls and each pilot has a quick-donning type of oxygen mask that can be placed on the face with one hand from the ready position within 5 seconds, supplying oxygen and properly secured and sealed.
(2) Notwithstanding paragraph (b)(1)(ii) of this section, if for any reason at any time it is necessary for one pilot to leave the controls of the aircraft when operating at flight altitudes above flight level 350, the remaining pilot at the controls shall put on and use an oxygen mask until the other pilot has returned to that crewmember's station.
Test yourself
Practice questions from our free FAA written test prep that cite 14 CFR 91.211.
Commercial Pilot
Above what cabin pressure altitude must the required minimum flight crew use supplemental oxygen for the entire flight time at that altitude?
- A. 14,000 feet MSL.
- B. 12,500 feet MSL.
- C. 15,000 feet MSL.
- D. 10,000 feet MSL.
Show answer
A. 14,000 feet MSL. Between 12,500 and 14,000 MSL the crew needs oxygen only for the portion over 30 minutes. Above 14,000 MSL the crew uses it the entire time, and above 15,000 MSL oxygen must be provided to each occupant: provided, not necessarily used.
More Commercial Pilot practice →Advanced Ground Instructor
In an unpressurized airplane, each occupant must be PROVIDED supplemental oxygen above a cabin pressure altitude of:
- A. 15,000 feet MSL.
- B. 12,500 feet MSL.
- C. 14,000 feet MSL.
- D. 18,000 feet MSL.
Show answer
A. 15,000 feet MSL. Three tiers: required minimum crew must use oxygen after 30 minutes above 12,500 up to and including 14,000; use it at all times above 14,000; and every occupant must be PROVIDED it above 15,000: provided, not necessarily using.
More Advanced Ground Instructor practice →Commercial Pilot
In a pressurized aircraft operating above flight level 350 with one pilot at the controls, that pilot must:
- A. wear and use an oxygen mask; the quick-donning exception at or below FL410 applies only when two pilots are at the controls.
- B. keep an oxygen mask within reach at all times but need not wear it.
- C. descend below FL350 within 30 minutes.
- D. have a second crewmember on the flight deck at all times.
Show answer
A. wear and use an oxygen mask; the quick-donning exception at or below FL410 applies only when two pilots are at the controls. 91.211(b) requires one pilot at the controls to wear and use a mask above FL350. The exception at or below FL410 applies only when two pilots are at the controls and each has a quick-donning mask; if one pilot leaves the controls above FL350, the remaining pilot must put on and use a mask until the other returns.
More Commercial Pilot practice →
Questions pilots ask
At what altitude is oxygen required?
For the required minimum flight crew, above 12,500 feet MSL cabin pressure altitude for the part of the flight at those altitudes of more than 30 minutes, and for the entire time above 14,000 feet (91.211(a)(1) and (a)(2)). Above 15,000 feet each occupant must be provided with oxygen (91.211(a)(3)).
Do passengers have to wear oxygen above 15,000 feet?
The rule requires that each occupant be provided with supplemental oxygen above 15,000 feet MSL cabin pressure altitude (91.211(a)(3)). The word "uses" appears only in the crew requirements of (a)(1) and (a)(2).
What does a pressurized airplane need above FL 250?
At least a 10-minute supply of supplemental oxygen for each occupant, in addition to any oxygen required by paragraph (a), for use if a descent is necessitated by loss of cabin pressurization (91.211(b)(1)(i)).