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The Pilots Desk
US-FAA14 CFR 91.803

Part 125 operators: Designation of applicable regulations

Read the official rule

This regulation clarifies which noise and emissions rules apply to Part 125 operators (large airplanes used for commercial purposes but not scheduled airline service).

The key principle is that the noise standards that applied to an airplane before November 29, 1980, continue to apply even when operated under Part 125. For airplanes that weren't operating in the U.S. before that date, different rules kick in: subsonic airplanes must meet the requirements in §91.805, while supersonic airplanes must comply with §§91.819 and 91.821.

Importantly, if a Part 125 operator receives approval to operate under a different part (like Part 121 or 135), these noise requirements still apply—the deviation doesn't exempt the airplane from meeting the applicable noise standards. This ensures consistent noise compliance regardless of operational changes.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*

This is an original plain-English explanation for training and reference, not legal advice and not for navigation. Always rely on the current official rule linked above. Last reviewed June 20, 2026.