Definition
A specific section of the U.S. federal aviation regulations that requires every U.S.-registered aircraft to display nationality and registration marks (the N-number) on the aircraft's exterior, and sets the rules for how those marks must appear, including their location, size, and legibility.
Plain English
It is the rule that says every U.S. aircraft must have its registration number painted on the outside, and tells the owner exactly where to put it and how big and clear it has to be.
Context Anchor
You may see this citation when reading about aircraft identification plates, registration markings, or whether an aircraft meets required marking rules during preflight review.
Derivation
CFR' stands for Code of Federal Regulations, the official collection of U.S. government rules. 'Title 14' is the part of that code dealing with Aeronautics and Space. 'Part 45' covers Identification and Registration Marking. 'Section 45.11' is the specific paragraph within that part that lists the marking requirements. So '14 CFR part 45, section 45.11' is simply an address pointing to one specific rule within the larger rulebook.
Why Pilots Care
Aircraft must carry compliant markings to be considered airworthy and legally flown; incorrect or missing marks can result in the airplane being grounded during inspection.
Intuition Check
“Part” here does not mean a physical airplane part. In a regulation citation, “part” means a group of rules, and “section” means one exact rule within that group.
Example Sentence 1
During preflight, the pilot verified that the N-number on the tail matched the registration certificate and was displayed in accordance with 14 CFR part 45, section 45.11.
Example Sentence 2
An FAA inspector checked the aircraft against 14 CFR part 45, section 45.11 during a ramp inspection to verify the markings were permanent and properly placed.