An FAA Advisory Circular is a document the Federal Aviation Administration publishes to explain how pilots, operators, manufacturers, and airports can meet federal aviation regulations. Advisory Circulars are not regulations. They describe methods the FAA considers acceptable for complying with a rule in Title 14 of the Code of Federal Regulations, and they are not binding on the public unless a specific regulation incorporates the circular by reference.1Federal Aviation Administration. Aeronautical Information Manual – Code of Federal Regulations and Advisory Circulars
What an Advisory Circular Is For
Federal Aviation Regulations, codified in Title 14 of the CFR, are often written in broad terms.2eCFR. Title 14 of the CFR – Aeronautics and Space A rule might require an aircraft to meet certain airworthiness standards without spelling out inspection intervals or torque values. Advisory Circulars fill that gap. They lay out specific procedures, technical practices, and methods the FAA has already evaluated and found acceptable for meeting a regulation’s requirements.3Federal Aviation Administration. FAA Order 1320.46D – FAA Advisory Circular System
The subject range is enormous: airworthiness standards, pilot and instructor certification, airport design, noise compatibility planning, air carrier operations, and much more. If a federal aviation rule applies to you, there is almost certainly an AC somewhere describing how the FAA expects that rule to be met in practice.
Are Advisory Circulars Legally Binding?
No. The FAA’s Aeronautical Information Manual states it plainly: “Unless incorporated into a regulation by reference, the contents of an advisory circular are not binding on the public.”1Federal Aviation Administration. Aeronautical Information Manual – Code of Federal Regulations and Advisory Circulars FAA Order 1320.46D, which governs the AC system internally, requires every AC to include language making clear that the circular “is not mandatory and does not constitute a regulation” and describes “an acceptable means, but not the only means” of compliance.3Federal Aviation Administration. FAA Order 1320.46D – FAA Advisory Circular System
The same order goes further: an AC “may not generally be used to add, reduce, or change a regulatory requirement.”3Federal Aviation Administration. FAA Order 1320.46D – FAA Advisory Circular System If you decide to follow the method described in an AC, you need to follow it in all important respects. But you are free to meet the underlying regulation a different way, as long as your approach achieves an equivalent level of safety.
When an Advisory Circular Becomes Mandatory
The one exception is incorporation by reference. When a regulation explicitly adopts an AC, the guidance in that circular becomes as enforceable as the regulation itself.
A clear example is 14 CFR 152.11, which governs the Airport Aid Program. That regulation states that the advisory circulars listed in its appendix “are incorporated into this part by reference” and designates them as “mandatory standards.” Even there, the regulation allows modifications for individual projects when local conditions demand it, provided the changes maintain an acceptable level of safety, economy, durability, and workmanship.4eCFR. 14 CFR 152.11 – Incorporation by Reference
If you are working under a regulation that incorporates an AC, read the regulation carefully. Incorporation by reference does not always sweep in the entire circular, and the regulation itself may carve out exceptions.
Why Following an AC Still Matters
Non-binding does not mean ignorable. In enforcement proceedings and litigation, an AC represents the FAA’s published view of what constitutes safe practice. If you deviate from an AC’s methods and something goes wrong, you will need to show that your alternative approach was equally safe. An operator who followed the AC to the letter is in a far stronger position during an investigation than one who improvised without documentation.
An AC works as a safe harbor. Following one does not guarantee you will never face scrutiny, but it gives you a well-documented defense. Departing from one is not prohibited, but doing so without a solid engineering or operational rationale invites trouble if the FAA or NTSB ever reviews your practices.
Proposing an Alternative Method of Compliance
Because ACs describe acceptable means rather than the only means, any person or organization can propose a different approach to meeting a regulation. The FAA evaluates alternatives by comparing them against the safety level the AC’s method would achieve. You need substantiating data showing your approach resolves the same safety concern the regulation addresses.
How formal the process is depends on context. For airworthiness directives, the FAA runs a structured Alternative Method of Compliance (AMOC) process under 14 CFR 39.19, requiring detailed technical descriptions, serial numbers, and supporting analysis.5Federal Aviation Administration. AC 39-10 – Advisory Circular For general operational ACs, the process is less formal, but the principle is the same: demonstrate equivalent safety, and document everything.
Reading an Advisory Circular Number
ACs follow a numbering system that mirrors the subject areas of Title 14 of the CFR. The first one or two digits identify the broad subject category:6Federal Aviation Administration. Appendix 1 Advisory Circular Numbering System
- 00 — General (definitions, abbreviations)
- 20 — Aircraft (airworthiness, maintenance, registration)
- 60 — Airmen (pilot certification, medical standards)
- 70 — Airspace (federal airways, special use airspace)
- 90 — Air Traffic and General Operating Rules
- 120 — Air Carrier Certification and Operations
- 150 — Airports (noise compatibility, airport aid)
After the subject number, a dash and a sequential number identify the specific circular within that series. AC 61-65 falls under the Airmen category and is the 65th circular in that series. When the FAA revises an AC, it appends a letter: the first revision becomes “A,” the second “B,” and so on. AC 61-65K is the eleventh revision of that circular.7Federal Aviation Administration. AC 61-65K – Certification: Pilots and Flight and Ground Instructors
Finding and Verifying a Current AC
The FAA maintains a searchable database of all Advisory Circulars on its website.8Federal Aviation Administration. Advisory Circulars You can search by AC number, title, description, or issuing office, and filter by status: active, canceled, or inactive.
Always check status before relying on an AC. A canceled or superseded circular may contain outdated methods that no longer reflect the FAA’s current position. The database shows each document’s status and issue date, so verifying currency takes only a moment and avoids the real risk of following guidance the FAA has already moved past.