Definition
A reference to a section of the Code of Federal Regulations dealing with aviation matters. The citation '4 CFR Part 89' as written is almost certainly a typographical or scanning error in the source, as Title 4 of the CFR covers Accounts (General Accounting Office matters), not aviation. The intended reference is most likely 14 CFR Part 89, which contains the FAA's rules for Remote Identification of Unmanned Aircraft (drones), requiring most drones operating in U.S. airspace to broadcast identification and location information.
Plain English
This is a federal rule book reference. As printed it appears to be a misprint; the real regulation pilots care about is 14 CFR Part 89, which sets the rules for how drones must broadcast their identity and location while flying.
Context Anchor
Seen in regulatory references, especially when the AIM points the reader to the federal rule that controls a topic.
Derivation
CFR stands for Code of Federal Regulations, the official collection of U.S. federal rules organized by Title and then by Part. Title 14 is the title that covers Aeronautics and Space, and Part 89 within Title 14 is the specific section on Remote Identification of Unmanned Aircraft.
Why Pilots Care
Pilots and operators must comply with this regulation to legally fly most unmanned aircraft and to avoid airspace violations or enforcement actions.
Intuition Check
Do not assume every “CFR Part 89” reference is an aviation rule. The title number matters: 14 CFR is the FAA aviation title; 4 CFR is a different title.
Example Sentence 1
Most drones operating in the National Airspace System must comply with 14 CFR Part 89 by broadcasting Remote ID information.
Example Sentence 2
The AIM glossary directs readers to 4 CFR Part 89 for the exact remote identification performance standards.