ADS-B In vs. Out: Requirements, Traffic and Weather

Last fact check: July 30, 2026

ADS-B Out and ADS-B In perform different jobs. ADS-B Out broadcasts information about your aircraft and is required when operating in airspace defined by 14 CFR 91.225. ADS-B In receives traffic and flight-information services for display in the cockpit, but the FAA does not generally require it.

That distinction explains why a portable receiver can add useful traffic and weather to a tablet but cannot make an aircraft compliant with the ADS-B Out rule. It also explains why an owner can install an Out-only transponder and later add In without replacing the compliance equipment.

The right setup depends on where the aircraft flies, its certification and electrical system, its current transponder and GPS position source, and where the pilot wants to display traffic and weather.

ADS-B In vs. Out at a glance

Capability	ADS-B Out	ADS-B In
Main function	Broadcasts aircraft identity, position, altitude, velocity and other data	Receives air-to-air ADS-B and eligible FAA rebroadcast or information services
Required by the FAA?	Yes, in the airspace specified by 14 CFR 91.225	No for ordinary general-aviation use
Portable device satisfies requirement?	No	A compatible portable receiver can provide advisory information
Frequencies used in the U.S.	1090ES or 978 UAT, subject to operating limits	A receiver may be single-band or dual-band
Weather	Does not itself display weather	FIS-B is transmitted on 978 UAT
Traffic	Makes the aircraft visible to compatible surveillance systems and receivers	Displays available ADS-B, ADS-R and TIS-B traffic, subject to limitations

What ADS-B Out does

Automatic Dependent Surveillance-Broadcast Out uses a qualified position source and installed avionics to broadcast an aircraft’s location and other information. “Automatic” means it operates without a pilot or controller interrogation. “Dependent” reflects its dependence on position and aircraft data. “Broadcast” means the message is transmitted for appropriate ground stations and nearby equipped aircraft to receive.

The system reports information more frequently and with greater precision than traditional rotating radar alone. Air traffic control can use compliant ADS-B Out as a surveillance source, while ADS-B In-equipped aircraft may receive the air-to-air broadcast directly.

Compliance is more than buying a transmitter. The installed system must use an approved configuration, transmit the correct aircraft and flight identification data, and meet the performance requirements of 14 CFR 91.227. A portable ADS-B transmitter is not a substitute for a compliant installed ADS-B Out system.

Where ADS-B Out is required

The statement “ADS-B Out is required in controlled airspace” is too broad. Much controlled airspace does not require it. The FAA identifies these primary U.S. rule-airspace categories:

all Class A airspace
Class B and Class C airspace
above the ceiling and within the lateral boundaries of Class B or Class C

airspace, up to 10,000 feet MSL

within the 30-nautical-mile Mode C veil around airports listed in 14 CFR

Part 91, Appendix D, generally from the surface to 10,000 feet MSL

Class E airspace at and above 10,000 feet MSL over the 48 contiguous states

and Washington, D.C., excluding airspace at and below 2,500 feet above the surface

Class E airspace at and above 3,000 feet MSL over the Gulf within 12 nautical

miles of the U.S. coastline

Certain aircraft not originally certificated with an engine-driven electrical system, and not subsequently certified with one, have exceptions subject to the exact operating location. Operators can also request authorization for a specific flight without compliant ADS-B Out, but the request has timing and ATC-approval requirements and should not be treated as routine equipage.

Use the FAA’s ADS-B airspace guidance and the actual language of 14 CFR 91.225 when planning operations. “Below 10,000 feet” by itself is not a reliable equipage test because Class B, Class C and Mode C veil requirements can apply well below that altitude.

What ADS-B In adds

ADS-B In receives information for a compatible cockpit display. Depending on the receiver, installation, coverage and client status, this can include:

direct air-to-air ADS-B traffic
ADS-R, which rebroadcasts traffic between the 1090ES and 978 UAT links
TIS-B, which sends eligible radar-derived traffic information from the

ground system

FIS-B weather and aeronautical products on 978 UAT

FIS-B includes products such as METARs, TAFs, graphical weather, PIREPs, NOTAMs, TFR information, AIRMETs, SIGMETs and winds aloft. The service is subscription-free, but the pilot still needs compatible receiving and display equipment.

ADS-B In may be installed in the panel or supplied by a portable receiver connected to a tablet or portable display. It remains advisory equipment unless a specific approved operation and installation says otherwise.

1090ES vs. 978 UAT

U.S. ADS-B uses two data links:

1090 MHz Extended Squitter, or 1090ES
978 MHz Universal Access Transceiver, or UAT

Aircraft operating in Class A airspace must use 1090ES. A compliant UAT Out installation can be an option for eligible aircraft that remain below 18,000 feet, while 1090ES is the internationally prevalent link and supports operations at any altitude when properly configured.

For ADS-B In, a dual-band receiver listens for traffic on both frequencies. FAA ADS-R can rebroadcast messages from one link onto the other when the aircraft meets the service criteria and is within ground coverage, but direct dual-band reception can provide the best opportunity to receive nearby ADS-B-equipped traffic without depending on that rebroadcast path.

FIS-B is broadcast on 978 UAT, not on 1090 MHz. A pilot who wants subscription-free FAA weather therefore needs equipment capable of receiving the UAT data link.

Correcting two common equipment mistakes

The Garmin GTX 335 and Appareo Stratus ESG are often mislabeled as UAT units. They are not.

The Garmin GTX 335 is a 1090ES ADS-B Out transponder. It does not contain the dual-band ADS-B In capability of the GTX 345.

The Garmin GTX 345 combines 1090ES ADS-B Out with dual-link 1090/978 ADS-B In. Depending on the exact version and installation, it can send traffic, weather, GPS and backup-attitude data to compatible displays and mobile apps.

The Appareo Stratus ES and ESG are also 1090ES ADS-B Out transponders. “Stratus” is a product family, so a panel transponder should not be confused with a portable Stratus ADS-B In receiver.

Always verify the complete part number, approved model list, position source, antenna requirements, display compatibility and installation approval with an avionics shop.

Why ADS-B In traffic is not TCAS

An ADS-B traffic display can materially improve situational awareness, but it is not accurate to describe every portable ADS-B In receiver as “TCAS for general aviation.”

Direct ADS-B reception shows aircraft that are transmitting compatible ADS-B Out. TIS-B can add certain transponder-equipped aircraft tracked by the ATC surveillance system. However:

aircraft without ADS-B Out or an operating transponder may not appear
primary-radar-only targets generally are not included
low-altitude radar and ground-station coverage can be limited
equipment configuration and ADS-B client status affect some rebroadcast

services

displayed position or trend information can be delayed or incomplete

The FAA describes TIS-B as an aid to visual acquisition, not a collision avoidance system. Pilots remain responsible for seeing and avoiding other aircraft under 14 CFR 91.113.

Understanding the traffic “hockey puck”

TIS-B and ADS-R services are designed around an eligible ADS-B Out client aircraft. The ground system provides traffic within a volume around that aircraft—commonly illustrated as a 30-nautical-mile-diameter “hockey puck” extending 3,500 feet above and below it.

An In-only aircraft may receive some air-to-air and ground traffic, but it should not assume it is receiving a complete customized traffic picture. ForeFlight, for example, warns that a Sentry used in an aircraft without ADS-B Out will show a limited traffic view.

This is a strong reason to understand the receiver’s status messages and user guide rather than treating every target-free screen as clear airspace.

ADS-B weather is strategic, not tactical

FIS-B weather is extremely useful for observing trends, evaluating the larger weather picture and making strategic diversion decisions. It is not suitable for close-range thunderstorm penetration or tactical maneuvering between cells.

The age shown on a cockpit display does not necessarily represent the age of the underlying observation, radar scan or composite. The FAA warns that in extreme cases displayed NEXRAD data can be as much as 15 minutes older than the age indication for that radar product.

Use current preflight and inflight weather information, understand each product’s update interval and latency, and leave generous margins around convective weather. ADS-B weather supplements—not replaces—sound weather briefing and airborne decision-making.

Installed vs. portable ADS-B In

A portable receiver is often the least disruptive way to add ADS-B In. Modern units may include dual-band traffic reception, UAT weather, GPS, AHRS, barometric pressure and a carbon-monoxide alarm. Compatibility is not universal: confirm that the receiver supplies the desired data to the exact app and device used in flight.

Portable advantages include:

no permanent installation for the receiver itself
easy movement between rental or club aircraft
an independent GPS or attitude source on equipped models
lower initial commitment than many panel integrations

Portable limitations include:

battery management and charging cables
antenna placement and airframe shielding
suction-mount or loose-object concerns
tablet heat and glare
possible lack of integration with installed audio or panel displays

An installed In solution can reduce cockpit clutter and place traffic or weather on certified displays, but capability depends on the complete installation. Some systems also stream data to mobile apps.

Choosing the right ADS-B setup

Use this sequence rather than shopping by product name:

Map the actual operations. Determine whether planned routes enter

14 CFR 91.225 rule airspace and whether flight above 18,000 feet requires 1090ES.

Inventory existing equipment. Record the transponder, approved GPS

position source, navigator, displays, antennas and portable devices.

Separate compliance from display goals. List ADS-B Out requirements

independently from desired traffic, weather, AHRS or app functions.

Choose the display path. Decide whether In information must appear on

the panel, tablet, portable navigator or more than one display.

Check exact compatibility. Confirm models, software versions, data

interfaces and supported mobile apps.

Obtain an installed quote. Labor and required components vary greatly

by aircraft and existing wiring; an advertised hardware price is not the installed cost.

Validate performance. After installation, follow the installer and

approval-data procedures and request an FAA Public ADS-B Performance Report for a suitable flight.

How to verify ADS-B Out after installation

The FAA’s Public ADS-B Performance Report, or PAPR, checks a detected flight against ADS-B performance metrics. The owner enters the flight date, aircraft identifier and equipment information, and the FAA emails the report.

Fly in published FAA ADS-B coverage with the correct transmitted flight identification. Operations near the surface or at the edge of coverage can produce misleading failures. Review any red-flagged category with the installer rather than changing configuration without approved guidance.

Request a Public ADS-B Performance Report after an appropriate post-installation flight and periodically when a performance concern arises.

Bottom line

You need ADS-B Out when your operation enters the airspace specified by 14 CFR 91.225. You do not need it merely because all controlled airspace is supposedly covered by the rule. The exact airspace and aircraft exceptions matter.

ADS-B In is optional for ordinary operations but highly useful. It can provide traffic and, with UAT reception, subscription-free weather and aeronautical information. Its displays remain subject to coverage, equipment, latency and traffic-source limitations.

For many owners, a compliant installed ADS-B Out system plus a compatible dual-band portable receiver is a flexible solution. For others, an integrated In/Out transponder and panel display are worth the installation cost. Choose by rule airspace, frequency, approved installation and display compatibility— not by assuming that every “ADS-B” product performs both jobs.

Related Aircraft Insider guides

Primary sources used

FAA, ADS-B frequently asked questions:

https://www.faa.gov/air_traffic/technology/equipadsb/resources/faq

FAA, ADS-B rule airspace:

https://www.faa.gov/air_traffic/technology/equipadsb/research/airspace

FAA, ADS-B In and Out:

https://www.faa.gov/air_traffic/technology/equipadsb/capabilities/ins_outs

FAA, ADS-B In pilot applications and FIS-B latency:

https://www.faa.gov/air_traffic/technology/adsb/pilot

FAA Aeronautical Information Manual, TIS-B capabilities and limitations:

https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap4_section_5.html

FAA Public ADS-B Performance Report:

https://adsbperformance.faa.gov/PAPRRequest.aspx

Electronic Code of Federal Regulations, 14 CFR 91.225:

https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-91/subpart-C/section-91.225

Garmin, GTX 335 product details:

https://www.garmin.com/en-US/p/140939/

Garmin, GTX 345 product details:

https://www.garmin.com/en-US/p/140949/

Appareo, Stratus ES/ESG pilot guide:

https://appareo.com/wp-content/uploads/2018/10/600890-000049-Stratus-ES-ESG-Pilots-Guide-FULL-PDF.pdf

ForeFlight, Sentry support and limitations:

https://www.foreflight.com/support/sentry/