# 14 C.F.R. § 91.851 (2026): Definitions > Federal · Regulations · In force URL: https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_851 ## Section - **Citation:** 14 C.F.R. § 91.851 (2026) - **Heading:** Definitions - **Jurisdiction:** Federal - **Kind:** Regulations - **Status:** In force - **Text as of:** August 14, 2026 - **Source:** Compiled text - **Location:** Title 14 CFR: Aeronautics and Space / Chapter I: FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION / Part 91: GENERAL OPERATING AND FLIGHT RULES / Subpart I: Operating Noise Limits / § 91.851: § 91.851 Definitions. ## Text For the purposes of §§ 91.851 through 91.877 of this subpart: Chapter 4 noise level means a noise level at or below the maximum noise level prescribed in Chapter 4, Paragraph 4.4, Maximum Noise Levels, of the International Civil Aviation Organization (ICAO) Annex 16, Volume I, Amendment 7, effective March 21, 2002. The Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 approved the incorporation by reference of this document, which can be obtained from the International Civil Aviation Organization (ICAO), Document Sales Unit, 999 University Street, Montreal, Quebec H3C 5H7, Canada. Also, you may obtain documents on the Internet at http://www.ICAO.int/eshop/index.cfm. Copies may be reviewed at the U.S. Department of Transportation, Docket Operations, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590 or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Contiguous United States means the area encompassed by the 48 contiguous United States and the District of Columbia. Fleet means those civil subsonic jet (turbojet) airplanes with a maximum certificated weight of more than 75,000 pounds that are listed on an operator's operations specifications as eligible for operation in the contiguous United States. Import means a change in ownership of an airplane from a non-U.S. person to a U.S. person when the airplane is brought into the United States for operation. Operations specifications means an enumeration of airplanes by type, model, series, and serial number operated by the operator or foreign air carrier on a given day, regardless of how or whether such airplanes are formally listed or designated by the operator hange in ownership of an airplane from a non-U.S. person to a U.S. person when the airplane is brought into the United States for operation. Operations specifications means an enumeration of airplanes by type, model, series, and serial number operated by the operator or foreign air carrier on a given day, regardless of how or whether such airplanes are formally listed or designated by the operator. Owner means any person that has indicia of ownership sufficient to register the airplane in the United States pursuant to part 47 of this chapter. New entrant means an air carrier or foreign air carrier that, on or before November 5, 1990, did not conduct operations under part 121 or 129 of this chapter using an airplane covered by this subpart to or from any airport in the contiguous United States, but that initiates such operation after that date. Stage 2 noise levels mean the requirements for Stage 2 noise levels as defined in part 36 of this chapter in effect on November 5, 1990. Stage 3 noise levels mean the requirements for Stage 3 noise levels as defined in part 36 of this chapter in effect on November 5, 1990. Stage 4 noise level means a noise level at or below the Stage 4 noise limit prescribed in part 36 of this chapter. Stage 2 airplane means a civil subsonic jet (turbojet) airplane with a maximum certificated weight of 75,000 pounds or more that complies with Stage 2 noise levels as defined in part 36 of this chapter. Stage 3 airplane means a civil subsonic jet (turbojet) airplane with a maximum certificated weight of 75,000 pounds or more that complies with Stage 3 noise levels as defined in part 36 of this chapter. Stage 4 airplane means an airplane that has been shown not to exceed the Stage 4 noise limit prescribed in part 36 of this chapter. A Stage 4 airplane complies with all of the noise operating rules of this part. Stage 5 airplane means an airplane that has been shown not to exceed the Stage 5 noise limit prescribed in part 36 of this chapter age 3 noise levels as defined in part 36 of this chapter. Stage 4 airplane means an airplane that has been shown not to exceed the Stage 4 noise limit prescribed in part 36 of this chapter. A Stage 4 airplane complies with all of the noise operating rules of this part. Stage 5 airplane means an airplane that has been shown not to exceed the Stage 5 noise limit prescribed in part 36 of this chapter. A Stage 5 airplane complies with all of the noise operating rules of this part. Stage 5 noise level means a noise level at or below the Stage 5 noise limit prescribed in part 36 of this chapter. [Docket 26433, 56 FR 48658, Sept. 25, 1991, as amended by Amdt. 91-252, 61 FR 66185, Dec. 16, 1996; Amdt. 91-275, 67 FR 45237, July 8, 2002; Amdt. 91-288, 70 FR 38749, July 5, 2005; 72 FR 68475, Dec. 5, 2007; Docket FAA-2015-3782, Amdt. 91-349, 82 FR 46132, Oct. 4, 2017] ## Nearby sections - [14 C.F.R. § 91.801 (2026) § 91.801 Applicability: Relation to part 36.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_801.md) - [14 C.F.R. § 91.803 (2026) § 91.803 Part 125 operators: Designation of applicable regulations.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_803.md) - [14 C.F.R. § 91.805 (2026) § 91.805 Final compliance: Subsonic airplanes.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_805.md) - [14 C.F.R. § 91.815 (2026) § 91.815 Agricultural and fire fighting airplanes: Noise operating limitations.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_815.md) - [14 C.F.R. § 91.817 (2026) § 91.817 Civil aircraft sonic boom.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_817.md) - [14 C.F.R. § 91.818 (2026) § 91.818 Special flight authorization to exceed Mach 1.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_818.md) - [14 C.F.R. § 91.819 (2026) § 91.819 Civil supersonic airplanes that do not comply with part 36.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_819.md) - [14 C.F.R. § 91.821 (2026) § 91.821 Civil supersonic airplanes: Noise limits.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_821.md) - [14 C.F.R. § 91.851 (2026) § 91.851 Definitions.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_851.md) - [14 C.F.R. § 91.853 (2026) § 91.853 Final compliance: Civil subsonic airplanes.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_853.md) - [14 C.F.R. § 91.855 (2026) § 91.855 Entry and nonaddition rule.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_855.md) - [14 C.F.R. § 91.857 (2026) § 91.857 Stage 2 operations outside of the 48 contiguous United States.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_857.md) - [14 C.F.R. § 91.858 (2026) § 91.858 Special flight authorizations for non-revenue Stage 2 operations.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_858.md) - [14 C.F.R. § 91.859 (2026) § 91.859 Modification to meet Stage 3, Stage 4, or Stage 5 noise levels.](https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_859.md) --- Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/CFR_T14_P91_S91_851. Check the current official text before relying on it. Not legal advice.