top of page

ADS-B and the Airspace Where It’s Required

Updated: Dec 19, 2025

Automatic Dependent Surveillance–Broadcast (ADS-B) has become a cornerstone of modern air traffic surveillance. Mandated by the FAA as part of the NextGen air traffic control system, ADS-B improves aircraft tracking accuracy, enhances situational awareness, and increases overall safety. However, many pilots still have questions about what ADS-B is, how it works, and where it’s required.


This article explains ADS-B in clear terms and breaks down the specific airspace where ADS-B Out is mandatory.



Study this full length lesson (video, podcast, flashcards, and quiz) here: Full Length Lesson >


What Is ADS-B?

ADS-B is a surveillance technology that allows aircraft to broadcast their position and other flight data using onboard avionics rather than relying solely on ground-based radar.


ADS-B relies on:

  • GPS position data

  • Aircraft broadcast transmissions

  • Ground stations and satellites to receive and relay information


There are two main components:

  • ADS-B Out: Transmits aircraft position, altitude, velocity, and identification

  • ADS-B In: Receives traffic and weather information (optional, not required)


ADS-B Out vs. ADS-B In

ADS-B Out (Required)

ADS-B Out continuously broadcasts:

  • Aircraft GPS position

  • Pressure altitude

  • Ground speed and track

  • Aircraft identification (call sign or tail number)


ADS-B Out is required by regulation in certain airspace.


ADS-B In (Optional)

ADS-B In allows pilots to receive:

  • Traffic information (TIS-B)

  • Weather data (FIS-B)


While highly beneficial, ADS-B In is not required by the FAA.


FAA ADS-B Requirements

ADS-B Out requirements are defined in 14 CFR §91.225. In general, ADS-B Out is required anywhere a Mode C transponder is required, with some additional details.


Airspace Where ADS-B Is Required

Class A Airspace

  • From 18,000 feet MSL to FL600

  • IFR operations only


All aircraft operating in Class A airspace must be equipped with ADS-B Out.


Class B Airspace

ADS-B Out is required:

  • Within all Class B airspace

  • Within the Mode C veil, which extends:

    • 30 nautical miles from the primary Class B airport

    • From the surface to 10,000 feet MSL


This applies to both VFR and IFR aircraft.


Class C Airspace

  • ADS-B Out is required within all Class C airspace

  • Applies to all aircraft, regardless of flight rules


Above 10,000 Feet MSL

ADS-B Out is required:

  • At or above 10,000 feet MSL

  • Excluding airspace below 2,500 feet AGL


This ensures enhanced surveillance for aircraft operating at higher altitudes with faster closure rates.


Other Designated Airspace

ADS-B Out is also required in:

  • Certain Class E airspace over the Gulf of Mexico (defined in FAA regulations)

  • Additional areas as specified by NOTAM or special rule


Pilots should always review current charts and regulatory guidance.


When ADS-B Is NOT Required

ADS-B Out is not required in:

  • Most Class D airspace

  • Class E airspace below 10,000 feet MSL

  • Class G airspace, unless otherwise specified


However, aircraft must still comply with transponder requirements where applicable.


Equipment Types: 1090ES and UAT

ADS-B Out systems operate on one of two approved technologies:


1090ES (Extended Squitter)

  • Used primarily by aircraft operating above 18,000 feet

  • Integrated with Mode S transponders

  • Common in turbine and high-performance aircraft


UAT (978 MHz)

  • Available for aircraft operating below 18,000 feet

  • Often more affordable for general aviation

  • Supports both ADS-B Out and In


Operating Without ADS-B

Aircraft without ADS-B Out may operate in ADS-B–required airspace only if:

  • ATC authorization is received prior to flight

  • Requests are made in advance (typically at least one hour)


Authorization is limited and not guaranteed.


Common Pilot Mistakes

  • Assuming ADS-B is optional everywhere

  • Confusing transponder requirements with ADS-B requirements

  • Flying into a Mode C veil without ADS-B Out

  • Incorrect aircraft identification programming


These mistakes can result in airspace violations and enforcement action.


Final Thoughts

ADS-B represents a major advancement in air traffic surveillance, offering more accurate tracking, improved traffic awareness, and enhanced safety. Understanding where ADS-B Out is required—and ensuring your equipment is properly installed and configured—is essential for legal and confident flight operations.


As airspace continues to evolve, ADS-B remains a foundational technology shaping the future of aviation safety and efficiency.



Study Full Aviation Courses:

wifiCFI's full suite of aviation courses has everything you need to go from brand new to flight instructor and airline pilot! Check out any of the courses below for free:


Study Courses:


Checkride Lesson Plans:


Teaching Courses:



 
 
bottom of page