Automatic Dependent Surveillance-broadcast (ads-b) Out Equipment and Use

Regulation Text

(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.

[Docket FAA-2007-29305, 75 FR 30193, May 28, 2010; Amdt. 91-314-A, 75 FR 37712, June 30, 2010, as amended by Amdt. 91-316, 75 FR 37712, June 30, 2010; Amdt. 91-336, 80 FR 6900, Feb. 9, 2015; Amdt. 91-336A, 80 FR 11537, Mar. 4, 2015; Amdt. 91-355, 84 FR 34287, July 18, 2019; Amdt. 91-361, 86 FR 4513, Jan. 15, 2021; Docket FAA-2023-1836, Amdt. 91-371, 88 FR 71476, Oct. 17, 2023; Amdt. 91-371B, 89 FR 33224, Apr. 29, 2024]

Research Notes

Section 91.225 — ADS-B Out equipment and use — is the rule that drove the 2020 ADS-B mandate. Every aircraft operating in airspace where a Mode C transponder is required must also have ADS-B Out.

Where ADS-B Out is required (paragraph b):

(b)(1) — Class A airspace (FL180+)
(b)(2) — Class B airspace AND the Mode C veil (within 30 NM of Class B primary airports, surface to 10,000 MSL)
(b)(3) — Class C airspace
(b)(4) — Above 10,000 MSL excluding the 2,500 AGL exception
(b)(5) — Class E airspace at or above 3,000 feet MSL over the Gulf of Mexico from the U.S. coast out to 12 NM

Two ADS-B Out 'links' — 1090ES vs UAT:

1090ES (Extended Squitter): Required in Class A airspace and recommended for aircraft operating internationally or above FL180. Uses the 1090 MHz transponder spectrum.
UAT (Universal Access Transceiver, 978 MHz): Permitted only below FL180. Provides FIS-B (Flight Information Service Broadcast — free weather + traffic data) on the same frequency.

Equipment performance requirements (paragraph d): The ADS-B Out equipment must transmit position, altitude, velocity, identification, and other data per TSO-C166b (1090ES) or TSO-C154c (UAT). Position source must meet specific accuracy requirements (typically WAAS GPS).

The 2020 mandate: § 91.225 took effect January 1, 2020. As of that date, ANY aircraft operating in the airspace listed above MUST have ADS-B Out. Aircraft without ADS-B Out cannot legally operate in those airspace classes.

'Below the floor' exception: ADS-B Out is NOT required for Class C/D airspace where it's not otherwise listed, nor at lower altitudes where Mode C is also not required. Many rural Class E areas don't require ADS-B Out.

The ADS-B failure procedure: If ADS-B Out fails in flight while operating in required airspace, the pilot may operate with prior ATC permission. The pilot calls ATC, reports the failure, and ATC may authorize continued operation in the airspace.

ADS-B In (free): ADS-B In (the receive-only side) is NOT mandated by § 91.225 but is increasingly common. The FAA's FIS-B service delivers free in-cockpit weather and traffic to UAT receivers. Apps like ForeFlight integrate this data with the cockpit display.

Reference: FAA ADS-B program; AC 90-114B on ADS-B operations; TSO-C166b and TSO-C154c.

ADS-B Out — Where It's Required, Decoded — § 91.225

Most pilots learned the Mode C veil first and got ADS-B Out bolted onto the lesson plan years later. That's backwards. As of January 1, 2020, § 91.225 stands on its own — it's not a footnote to § 91.215. The required airspace looks similar (and that's not an accident — the FAA wrote the two regs to align), but ADS-B Out is its own mandate, with its own equipment rules and its own enforcement teeth.

Here's where you must have it transmitting:

Airspace	ADS-B Out required?	Why
Class A	Yes — and it must be 1090ES	Above FL180 the rule is 1090 MHz Extended Squitter only. UAT is not authorized.
Class B (surface to ceiling)	Yes	1090ES or 978 UAT, your choice below FL180.
Class C (surface to ceiling)	Yes	Same — pick a link.
Mode C veil (30 nm of a Class B primary, surface to 10,000 MSL)	Yes	This is the same lateral footprint as § 91.215 — the FAA didn't reinvent the geometry.
Above 10,000 MSL in the 48 contiguous states (excluding airspace at and below 2,500 AGL)	Yes	The 2,500-AGL carve-out is the part most pilots forget. Cross the Rockies VFR at 11,500 over a 9,500-foot ridge and you're inside the carve-out — but climb 1,500 more feet and you're not.
Class E over the Gulf of Mexico, at and above 3,000 MSL, within 12 nm of the U.S. coast	Yes	The offshore rule most CFIs gloss over.

The two links — pick one, but pick correctly:

1090ES (1090 MHz Extended Squitter) — international standard, required above FL180, legal everywhere below. If you ever fly outside the U.S. or above Class A, this is the only choice.
978 UAT (Universal Access Transceiver) — U.S.-only, below FL180 only. The trade-off: UAT gives you free FIS-B weather and TIS-B traffic in if you also have ADS-B In equipment, which 1090ES does not.

Per § 91.225(g), your position source must be a WAAS-capable GPS meeting the TSO-C145/C146 performance standard. A non-WAAS GPS will not satisfy this rule — the integrity numbers it broadcasts won't pass FAA conformance.

One more thing the test prep books bury: § 91.225 is "ADS-B Out" only — broadcast position to the FAA. ADS-B In (the receive side that gives you weather and traffic on your iPad) is not required by any reg. It's a capability, not a mandate.

What an Examiner Asks About § 91.225

DPEs don't ask "what does ADS-B do" anymore. They ask the questions that reveal whether you actually understand the airspace map.

"Where is ADS-B Out required?" — Class A, B, C, the Mode C veil, above 10,000 MSL with the 2,500-AGL carve-out, and the Gulf shelf. If you skip the carve-out or the Gulf, you're 50% there.
"What's the difference between 978 UAT and 1090ES?" — Frequency, altitude ceiling (UAT is U.S.-only, below FL180), and the In-services side benefit. The DPE wants the altitude line, especially.
"Is ADS-B In required?" — No. Not by § 91.225, not by any other Part 91 reg. It's optional capability. Don't let the question pressure you into the wrong answer.
"Can you fly without ADS-B Out into rule airspace?" — Only with prior ATC authorization under § 91.225(g) — you request a deviation, ATC issues one (or doesn't), and you fly the deviation. It's not a "broken on the ramp, we'll figure it out airborne" situation.
The trick question: "You're at 9,500 MSL VFR over terrain that's 8,000 MSL — do you need ADS-B Out?" The Mode C veil and Class B/C answer that locally. Above 10,000 MSL, the 2,500-AGL carve-out kicks in — so over an 8,000-foot ridge, you have until 10,500 MSL before the above-10,000 rule grabs you. Know the math.

Flying ADS-B-Equipped, Under § 91.225

Picture this: VFR cross-country at 9,500 MSL, headed across a Class B Mode C veil to get to the airport on the other side. You're not talking to anyone — VFR, not entering the Class B itself, just clipping the 30-nm shelf at altitude.

Your ADS-B Out is transmitting the whole time. Your N-number, your position to within a few meters, your altitude, your velocity vector — every second, to anyone listening. ATC sees you on their scope even though you never called them. If you have ADS-B In on board, your traffic display shows the Cessna 500 feet below and a mile ahead that you'd never have spotted visually against the terrain. That's the operational win — ADS-B isn't just paperwork; it's a real situational-awareness upgrade if you actually look at the screen.

Now the warning. Lateral noncompliance under ADS-B Out creates what controllers and FSDOs quietly call "violation by automation." If you bust the Class B floor by 200 feet, the old system needed a controller to notice and write it up. ADS-B logs your exact track at 1-second resolution to the FAA's data feed. The tag itself is the evidence. Pilots who used to get away with "I was on the line" don't anymore — the line is now a recording.

The fix isn't to fly without ADS-B (you can't, under § 91.225). The fix is to fly like the FAA is watching — because they literally are. Brief the airspace, brief the floors, set your altimeter, and treat every shelf as a hard wall, not a soft suggestion. ADS-B made the airspace safer. It also made it less forgiving. Both are true.

Amendment History

Amendment History Coming Soon

Every time this regulation changes, we'll record it here — the date, what was amended, and a plain-English summary of what shifted.