Definition
A specific federal regulation requiring that no person may operate a civil aircraft unless the airworthiness certificate is displayed at the cabin or cockpit entrance so that it is legible to passengers or crew. It is found in Title 14 of the Code of Federal Regulations, Part 91 (General Operating and Flight Rules), Section 91.203, paragraph (b).
Plain English
It's the rule that says the aircraft's airworthiness certificate must be posted near the cabin or cockpit door where passengers and crew can read it.
Context Anchor
Seen when learning required aircraft documents, checking aircraft paperwork during preflight, or reviewing FAA operating rules for a civil aircraft.
Derivation
CFR stands for Code of Federal Regulations, the published collection of rules made by U.S. federal agencies. Title 14 covers Aeronautics and Space. Part 91 is the section of those rules that governs general flight operations. The number after the decimal (91.203) identifies the specific rule, and the letter in parentheses (b) identifies the paragraph within that rule.
Why Pilots Care
Failure to display the certificate correctly can result in an FAA violation during a ramp check or inspection.
Intuition Check
Do not read “part” and “section” as loose page labels. In FAA regulations, they point to exact places in the law; “(b)” means paragraph b within section 91.203.
Example Sentence 1
During preflight, the pilot confirmed the airworthiness certificate was posted at the cabin entrance as required by 14 CFR part 91, section 91.203(b).
Example Sentence 2
During the ramp check the inspector confirmed the certificate met the display requirements of 14 CFR part 91, section 91.203(b).