Where ADS-B Out is required14 CFR 91.225 Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipment and use
After January 1, 2020, ADS-B Out is required in Class A, B and C airspace, within 30 nautical miles of the airports listed in appendix D, section 1, from the surface to 10,000 feet MSL, above the ceiling of Class B and C airspace (within their lateral boundaries) up to 10,000 feet MSL, and in Class E airspace at and above 10,000 feet MSL in the 48 contiguous states and DC (excluding at and below 2,500 feet above the surface), plus parts of the Gulf of Mexico.
By the ATIS Alerts team · Updated October 15, 2026 · Regulation text current as of October 14, 2026. A study aid based on the official regulation text, not legal advice or an FAA interpretation.
At a glance
- Class A: 1090 MHz extended squitter equipment (TSO-C166b or TSO-C166c) meeting 91.227 (a).
- Below 18,000 feet MSL in the (d) airspace: either 1090 MHz equipment or 978 MHz UAT equipment (TSO-C154c or TSO-C154d) meeting 91.227 (b).
- Class B and Class C airspace, and above their ceilings within their lateral boundaries up to 10,000 feet MSL (d)(1) and (d)(3).
- Within 30 nautical miles of an appendix D, section 1 airport, surface to 10,000 feet MSL (d)(2).
- Class E in the 48 contiguous states and DC at and above 10,000 feet MSL, excluding at and below 2,500 feet above the surface (d)(4); Class E at and above 3,000 feet MSL over the Gulf of Mexico out to 12 nautical miles (d)(5).
- If equipped, ADS-B Out must transmit at all times unless the FAA authorizes or ATC directs otherwise (f).
In plain English
Section 91.225 sets where an aircraft needs ADS-B Out equipment, unless ATC authorizes otherwise. The equipment must meet one of the listed technical standards and the performance requirements of 91.227. In Class A airspace, paragraph (a) accepts only TSO-C166b or TSO-C166c equipment, which paragraph (i) identifies as 1090 MHz extended squitter. Below 18,000 feet MSL, paragraph (b) also accepts TSO-C154c or TSO-C154d, the 978 MHz Universal Access Transceiver (UAT).
The airspace below 18,000 feet MSL where ADS-B Out is required is listed in (d): Class B and Class C airspace areas; within 30 nautical miles of an airport listed in appendix D, section 1, from the surface upward to 10,000 feet MSL; above the ceiling and within the lateral boundaries of a Class B or Class C airspace area upward to 10,000 feet MSL; Class E airspace within the 48 contiguous states and the District of Columbia at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet above the surface; and Class E airspace at and above 3,000 feet MSL over the Gulf of Mexico from the U.S. coastline out to 12 nautical miles.
Paragraph (e) gives relief to aircraft not originally certificated with an engine-driven electrical system (and not since certified with one), including balloons and gliders. They may operate without ADS-B Out in the Class E airspace in (d)(4), and within the 30-nautical-mile area in (d)(2) if they stay outside Class B and C airspace and below the ceiling of the Class B or C airspace or 10,000 feet MSL, whichever is lower.
Paragraph (f) requires an aircraft equipped with ADS-B Out to operate it in transmit mode at all times, unless the FAA authorizes otherwise for certain sensitive government missions or ATC directs otherwise. Paragraph (g) sets the timing for deviation requests: at any time for an inoperative ADS-B Out going to the destination or a repair location, and at least 1 hour before the operation for an aircraft not equipped. Section 91.225 does not mention transponders, so the separate transponder rules in 91.215 still apply on their own.
Common mistakes
- Assuming a 978 MHz UAT unit is enough in Class A. Paragraph (a) lists only TSO-C166b and TSO-C166c (1090 MHz) equipment.
- Treating the ADS-B and transponder airspace lists as identical. The Gulf of Mexico area (d)(5) appears only in 91.225, and the appendix D, section 2 area appears only in 91.215(b)(5)(ii).
- Forgetting the 2,500-foot exception in (d)(4), which excludes Class E airspace at and below 2,500 feet above the surface.
The official text
14 CFR 91.225 as published on the eCFR, current as of October 14, 2026.
(a) After January 1, 2020, unless otherwise authorized by ATC, no person may operate an aircraft in Class A airspace unless the aircraft has equipment installed that—
(1) Meets the performance requirements in-
(i) TSO-C166b and Section 2 of RTCA DO-260B (as referenced in TSO-C166b); or
(ii) TSO-C166c and Section 2 of RTCA DO-260C as modified by DO-260C—Change 1 (as referenced in TSO-C166c); and
(2) Meets the requirements of § 91.227.
(b) After January 1, 2020, except as prohibited in paragraph (h)(2) of this section or unless otherwise authorized by ATC, no person may operate an aircraft below 18,000 feet MSL and in airspace described in paragraph (d) of this section unless the aircraft has equipment installed that—
(1) Meets the performance requirements in—
(i) TSO-C166b and Section 2 of RTCA DO-260B (as referenced in TSO-C166b);
(ii) TSO-C166c and Section 2 of RTCA DO-260C as modified by DO-260C—Change 1 (as referenced in TSO-C166c);
(iii) TSO-C154c and Section 2 of RTCA DO-282B (as referenced in TSO-C154c); or
(iv) TSO-C154d and Section 2 of RTCA DO-282C (as referenced in TSO-C154d);
(2) Meets the requirements of § 91.227.
(c) Operators with equipment installed with an approved deviation under § 21.618 of this chapter also are in compliance with this section.
(d) After January 1, 2020, except as prohibited in paragraph (h)(2) of this section or unless otherwise authorized by ATC, no person may operate an aircraft in the following airspace unless the aircraft has equipment installed that meets the requirements in paragraph (b) of this section:
(1) Class B and Class C airspace areas;
(2) Except as provided for in paragraph (e) of this section, within 30 nautical miles of an airport listed in appendix D, section 1 to this part from the surface upward to 10,000 feet MSL;
(3) Above the ceiling and within the lateral boundaries of a Class B or Class C airspace area designated for an airport upward to 10,000 feet MSL;
(4) Except as provided in paragraph (e) of this section, Class E airspace within the 48 contiguous states and the District of Columbia at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet above the surface; and
(5) Class E airspace at and above 3,000 feet MSL over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles.
(e) The requirements of paragraph (b) of this section do not apply to any aircraft that was not originally certificated with an engine-driven electrical system, or that has not subsequently been certified with such a system installed, including balloons and gliders. These aircraft may conduct operations without ADS-B Out in the airspace specified in paragraph (d)(4) of this section. These aircraft may also conduct operations in the airspace specified in paragraph (d)(2) of this section if those operations are conducted—
(1) Outside any Class B or Class C airspace area; and
(2) Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport, or 10,000 feet MSL, whichever is lower.
(f) Except as prohibited in paragraph (h)(2) of this section, each person operating an aircraft equipped with ADS-B Out must operate this equipment in the transmit mode at all times unless—
(1) Otherwise authorized by the FAA when the aircraft is performing a sensitive government mission for national defense, homeland security, intelligence or law enforcement purposes and transmitting would compromise the operations security of the mission or pose a safety risk to the aircraft, crew, or people and property in the air or on the ground; or
(2) Otherwise directed by ATC when transmitting would jeopardize the safe execution of air traffic control functions.
(g) Requests for ATC authorized deviations from the requirements of this section must be made to the ATC facility having jurisdiction over the concerned airspace within the time periods specified as follows:
(1) For operation of an aircraft with an inoperative ADS-B Out, to the airport of ultimate destination, including any intermediate stops, or to proceed to a place where suitable repairs can be made or both, the request may be made at any time.
(2) For operation of an aircraft that is not equipped with ADS-B Out, the request must be made at least 1 hour before the proposed operation.
(h) For unmanned aircraft:
(1) No person may operate an unmanned aircraft under a flight plan and in two way communication with ATC unless:
(i) That aircraft has equipment installed that meets the performance requirements in TSO-C166b (including Section 2 of RTCA DO-260B, as referenced in TSO-C166b), TSO-C166c (including Section 2 of RTCA DO-260C as modified by DO-260C—Change 1, as referenced in TSO-C166c), TSO-C154c (including Section 2 of RTCA DO-282B, as referenced in TSO-C154c), or TSO-C154d (including Section 2 of RTCA DO-282C, as referenced in TSO-C154d); and
(ii) The equipment meets the requirements of § 91.227.
(2) No person may operate an unmanned aircraft under this part with Automatic Dependent Surveillance-Broadcast Out equipment in transmit mode unless:
(i) The operation is conducted under a flight plan and the person operating that unmanned aircraft maintains two-way communication with ATC; or
(ii) The use of ADS-B Out is otherwise authorized by the Administrator.
(i) The standards required in this section are incorporated by reference with the approval of the Director of the Office of the Federal Register under 5 U.S.C. 552(a) and 1 CFR part 51. This incorporation by reference (IBR) material is available for inspection at the FAA and the National Archives and Records Administration (NARA). Contact the FAA at: Office of Rulemaking (ARM-1), 800 Independence Avenue SW, Washington, DC 20590 (telephone 202-267-9677). For information on the availability of this material at NARA, visit https://www.archives.gov/federal-register/cfr/ibr-locations.html or email fr.inspection@nara.gov. This material is also available from the following sources in this paragraph (i).
(1) U.S. Department of Transportation, Subsequent Distribution Office, DOT Warehouse M30, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, MD 20785; telephone (301) 322-5377; website: www.faa.gov/aircraft/air_cert/design_approvals/tso/ (select the link “Search Technical Standard Orders”).
(i) TSO-C166b, Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Service-Broadcast (TIS-B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz), December 2, 2009.
(ii) TSO-C166c, Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Service-Broadcast (TIS-B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz), March 10, 2023.
(iii) TSO-C154c, Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B) Equipment Operating on the Frequency of 978 MHz, December 2, 2009.
(iv) TSO-C154d, Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B) Equipment Operating on the Radio Frequency of 978 Megahertz (MHz), March 10, 2023.
(2) RTCA, Inc., 1150 18th St. NW, Suite 910, Washington, DC 20036; telephone (202) 833-9339; website: www.rtca.org/products.
(i) RTCA DO-260B, Minimum Operational Performance Standards for 1090 MHz Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Services-Broadcast (TIS-B), Section 2, Equipment Performance Requirements and Test Procedures, December 2, 2009.
(ii) RTCA DO-260C, Minimum Operational Performance Standards for 1090 MHz Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Services-Broadcast (TIS-B), Section 2, Equipment Performance Requirements and Test Procedures, December 17, 2020.
(iii) RTCA DO-260C, Minimum Operational Performance Standards for 1090 MHz Extended Squitter Automatic Dependent Surveillance—Broadcast (ADS-B) and Traffic Information Services—Broadcast (TIS-B), Change 1, January 25, 2022.
(iv) RTCA DO-282B, Minimum Operational Performance Standards for Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B), Section 2, Equipment Performance Requirements and Test Procedures, December 2, 2009.
(v) RTCA DO-282C, Minimum Operational Performance Standards (MOPS) for Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B), Section 2, Equipment Performance Requirements and Test Procedures, June 23, 2022.
Test yourself
Practice questions from our free FAA written test prep that cite 14 CFR 91.225.
Commercial Pilot
ADS-B Out is required in which airspace?
- A. Class A, B, and C; above the ceiling of Class B up to 10,000 MSL; and generally at and above 10,000 feet MSL excluding airspace at and below 2,500 feet AGL.
- B. All controlled airspace at any altitude.
- C. Class D airspace only.
- D. Only above 18,000 feet MSL.
Show answer
A. Class A, B, and C; above the ceiling of Class B up to 10,000 MSL; and generally at and above 10,000 feet MSL excluding airspace at and below 2,500 feet AGL. 91.225 mirrors the Mode C transponder rule closely: Class A, B, and C, the Mode C veil around Class B, above 10,000 MSL except within 2,500 AGL, and over the Gulf of Mexico above 3,000 MSL within 12 NM of the coast.
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Questions pilots ask
Where is ADS-B Out required?
Class A (91.225(a)), and below 18,000 feet MSL in Class B and C airspace, within 30 nautical miles of appendix D, section 1 airports up to 10,000 feet MSL, above Class B and C ceilings within their lateral boundaries up to 10,000 feet MSL, Class E at and above 10,000 feet MSL in the 48 contiguous states and DC excluding at and below 2,500 feet above the surface, and Class E at and above 3,000 feet MSL over the Gulf of Mexico out to 12 nautical miles (91.225(d)).
Can I use a UAT (978 MHz) ADS-B unit?
Below 18,000 feet MSL, yes: 91.225(b)(1)(iii) and (iv) accept TSO-C154c and TSO-C154d equipment. In Class A, 91.225(a) accepts only TSO-C166b or TSO-C166c (1090 MHz) equipment.
Do I need ADS-B Out in Class D airspace?
Class D is not in the list in 91.225(d), but a Class D airport can lie within an area that is, such as within 30 nautical miles of an appendix D, section 1 airport (d)(2).
Can I fly without ADS-B Out in the required airspace?
Apart from the relief in 91.225(e) for aircraft not originally certificated with an engine-driven electrical system, only with an ATC authorized deviation. For an inoperative ADS-B Out, the request may be made at any time; for an aircraft not equipped, at least 1 hour before the proposed operation (91.225(g)).