Automatic Dependent Surveillance-Broadcast is a primary technology supporting the FAA’s Next Generation Air Transportation System, or NextGen, which shifts aircraft separation and air traffic control from ground-based radar to satellite-derived positions. ADS-B Out broadcasts an aircraft’s WAAS-enhanced GPS position to the ground, where it is displayed to air traffic controllers. It’s also transmitted to aircraft with ADS-B receivers, either directly or relayed by ground stations, increasing the pilot’s situational awareness.
In the continental United States, ADS-B Out has been required since January 2, 2020, for flight in:
Whether you’ve just decided to install ADS-B or have acquired an aircraft that’s not equipped, AOPA has resources to help you.
Without ADS-B Out, you can fly in any airspace except the ADS-B rule airspace defined by FAR 91.225 (see above). Note that ADS-B is not required in Class D airspace, or under a Class B or Class C airspace shelf, unless it lies within a Mode C veil. Keep in mind that ADS-B is mandated in a growing number of other countries.
Operators of aircraft not equipped with ADS-B Out, or with inoperative ADS-B Out, who wish to operate in ADS-B rule airspace must obtain an ATC authorization before flying. This must be requested online, at least one hour but not more than 24 hours before the intended flight, using the FAA’s ADS-B Deviation Authorization Preflight Tool (ADAPT). ADAPT is available only to aircraft with functioning, altitude-encoding transponders.
If your ADS-B fails in flight, you can continue to your destination, and ATC will coordinate with any subsequent ATC facilities along the remaining route of flight. If your ADS-B has failed, you’re on the ground, and you need access to ADS-B rule airspace, you’ll need to request an authorization through ADAPT (see above).
The FAA attempts to contact owners of aircraft transmitting erroneous or hazardously misleading ADS-B data but if the owner doesn’t respond—he or she may not receive the letter—the aircraft is added to the ADS-B No Services Aircraft List (NSAL). Controllers will not see its ADS-B data and the aircraft will not receive ADS-B-based ATC services. Aircraft on the NSAL cannot fly in ADS-B rule airspace without an ADAPT authorization.
Pilots flying an aircraft not certified with an engine-driven electrical system are exempt from portions of the ADS-B Out requirement, and can continue flying in the same airspace they fly without a transponder. For example, these aircraft can fly within the Mode C veil and no authorization is required. However, they must obtain authorization before entering Class B or Class C airspace by calling the ATC facility responsible for that airspace. For long-term access they can request a Letter of Agreement (LOA), which eliminates the need for individual authorizations. For assistance finding contact information for a specific ATC facility, email firstname.lastname@example.org
Most 978UATs have an Anonymous mode that you can use any time you’re not on an IFR flight plan or receiving air traffic services and are squawking a 1200 transponder code; you can file and activate a VFR flight plan. Consult the flight manual supplement for your equipment.
The FAA’s Privacy ICAO Address (PIA) program provides operators of 1090ES-equipped aircraft with an alternate, temporary ICAO aircraft address not associated with the owner in the Civil Aviation Registry, increasing privacy of their operations. A third-party call sign is required and can be obtained from FltPlan.com ($250 per year per aircraft); ForeFlight (one free with a Performance Plus or Business Performance subscription), or FlightAware (free to FlightAware Global subscribers). FltPlan.com and ForeFlight require flight plans to be filed through their respective services. You will need alternate flight identification issued by an FAA-approved third-party provider—the callsign—and a recent PAPR to complete the FAA's PIA application online.
AOPA’s online tool evaluates the kind of flying you do and helps steer you to the appropriate datalink(s). Links on this page offer more information about a wide array of ADS-B topics.
ADS-B Out—required in the ADS-B rule airspace defined by FAR 91.225—broadcasts GPS position to ground stations and directly to equipped aircraft.
ADS-B In—which is optional—generally refers to transmission of weather and traffic information from ground stations into the cockpit, where it can be displayed on panel-mounted avionics or a tablet, such as an iPad.
There are two paths to compliance, 978UAT or 1090ES, which are simply different ADS-B datalink options. A Universal Access Transceiver, or UAT, operates on 978 MHz (978UAT). This frequency receives free weather information, although not all UATs support the optional ADS-B In.
The 1090ES datalink uses a Mode S Extended Squitter transponder (1090 MHz; “ES” refers to ADS-B information appended to the Mode S data through an extended squitter). 1090ES is required above 18,000 feet and by the growing number of countries outside of the United States with ADS-B mandates. However, 1090ES does not receive weather data.