FAR 91.144 — High Barometric Pressure Restrictions
FAR 91.144 explains flight operation restrictions when barometric pressure exceeds 31 inches of mercury. Key rule for pilot students prepping for checkrides.
In Plain English
FAR 91.144 addresses a rare but important situation: when barometric pressure exceeds 31.00 inches of mercury along your route of flight. Most altimeters can't be set above 31.00 inHg, which means in unusually high-pressure conditions your altimeter will read lower than your true altitude — a serious terrain and traffic separation hazard.
Key points:
- If any information indicates that barometric pressure on your route currently exceeds, or will exceed, 31 inches of mercury, you may not operate an aircraft or begin a flight contrary to requirements published in a NOTAM issued under this section.
- The FAA issues a special Notice to Airmen (NOTAM) spelling out the operational procedures (such as altimeter setting and altitude correction guidance) that pilots must follow during these conditions.
- The Administrator may waive the restriction to allow emergency supply, transport, or medical services to isolated communities, provided the flight can be conducted with an acceptable level of safety.
Operationally, this matters because flying with an altimeter pegged at 31.00 while actual pressure is higher causes the indicated altitude to be lower than reality — risking CFIT and loss of separation in IFR conditions.
Regulation Text
14 CFR § 91.144§ 91.144 Temporary restriction on flight operations during abnormally high barometric pressure conditions.
(a)When any information indicates that barometric pressure on the route of flight currently exceeds or will exceed 31 inches of mercury, no person may operate an aircraft or initiate a flight contrary to the requirements established by the Administrator and published in a Notice to Airmen issued under this section.
(b)The Administrator is authorized to waive any restriction issued under paragraph (a) of this section to permit emergency supply, transport, or medical services to be delivered to isolated communities, where the operation can be conducted with an acceptable level of safety.
[Amdt. 91-240, 59 FR 17452, Apr. 12, 1994; 59 FR 37669, July 25, 1994]
Oral Exam Questions a DPE Might Ask
Q1What does FAR 91.144 require when barometric pressure on your route exceeds 31 inches of mercury?
Per FAR 91.144, you may not operate an aircraft or initiate a flight contrary to the requirements published by the FAA in a NOTAM issued for those high-pressure conditions.
Q2How does the FAA notify pilots of the special procedures for flight when pressure exceeds 31.00 inHg?
FAR 91.144 states the Administrator publishes the requirements in a Notice to Airmen (NOTAM), which pilots must comply with before and during the flight.
Q3Can the FAA ever waive the high-pressure flight restriction in FAR 91.144?
Yes. FAR 91.144(b) authorizes the Administrator to waive the restriction to permit emergency supply, transport, or medical services to isolated communities when the flight can be conducted with an acceptable level of safety.
Studying for a checkride?
Related Sections in Part 91