§ 91.123 Compliance with ATC clearances and instructions
14 CFR Part 91 — Subpart B—Flight Rules
Official text — 14 CFR § 91.123
REGULATION — LEGALLY BINDING(a) When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory. However, except in Class A airspace, a pilot may cancel an IFR flight plan if the operation is being conducted in VFR weather conditions. When a pilot is uncertain of an ATC clearance, that pilot shall immediately request clarification from ATC.
(b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised.
(c) Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible.
(d) Each pilot in command who (though not deviating from a rule of this subpart) is given priority by ATC in an emergency, shall submit a detailed report of that emergency within 48 hours to the manager of that ATC facility, if requested by ATC.
(e) Unless otherwise authorized by ATC, no person operating an aircraft may operate that aircraft according to any clearance or instruction that has been issued to the pilot of another aircraft for radar air traffic control purposes.
Reproduced from the eCFR. Text as amended through 2026-07-31. Verify against the official source before relying on it operationally.
SkeyeMentor explanation
Educational — not an FAA sourceIn plain English
Compliance with ATC clearances and instructions, when a pilot may deviate, and the reporting obligations that follow a deviation or a request for priority.
Why it matters
It is the counterpart to 91.3: it defines the limits of pilot authority when operating in controlled airspace.
Common mistake
Forgetting the requirement to notify ATC as soon as possible after deviating from a clearance in an emergency, and to submit a written report on request.
Quick example
ATC issues a clearance you believe is unsafe. Read paragraph (a) and describe your options.
Written and reviewed by the SkeyeMentor editorial team. This explanation is a study aid, not legal advice, and it is not part of the official text above. Verify current requirements through the official source before relying on them operationally.
Is this a regulation?
Yes — this is regulatory text and is legally binding.
Text published in the Code of Federal Regulations. Regulations are legally binding on pilots and operators.
Yes — this is the text of a Federal Aviation Regulation. It is legally binding. The explanation below it is SkeyeMentor educational content, not part of the regulation.