Definition
An Advisory Circular is a non-regulatory document issued by the Federal Aviation Administration that provides guidance, recommended practices, methods, and information on a specific aviation subject. ACs are numbered to correspond to the subject area in the Federal Aviation Regulations (for example, AC 90-23 relates to Part 90-series subjects such as wake turbulence). They explain how to comply with regulations, but they do not themselves create binding rules.
Plain English
An official FAA document that explains and recommends how to do something in aviation. It offers helpful guidance, but it is not a law you must follow.
Context Anchor
Seen in FAA handbooks, training materials, aircraft operations guidance, and instructor references when the FAA points pilots to more detailed guidance on a subject.
Derivation
‘Advisory’ comes from the Latin advisare, meaning ‘to give counsel.’ ‘Circular’ refers to a document circulated to a wide audience. Together, the name reflects exactly what these documents are: counsel that the FAA circulates to the aviation community.
Why Pilots Care
Pilots rely on Advisory Circulars for practical explanations that improve safety and decision-making beyond what regulations alone require.
Intuition Check
Do not read advisory as casual or unimportant. In FAA use, an Advisory Circular is official guidance, even though it is usually not a regulation by itself.
Example Sentence 1
Before flying behind a heavy jet, the instructor pointed his student to the Advisory Circular on wake turbulence for recommended spacing and takeoff techniques.
Example Sentence 2
Advisory Circulars are updated over time to share new safety recommendations with the aviation community.