Every second, commercial aircraft broadcast their position to the world.
Speed, altitude, location and flight ID are all transmitted automatically, once per second, to air traffic control and anyone else equipped to receive it. That's made possible by ADS-B Out: a technology most industry professionals will be familiar with that has been mandatory in US-controlled airspace since 2020.
ADS-B In is different, but equally important.
Two halves of the same system
ADS-B Out is like a beacon sent from an aircraft that makes it ‘visible’.
ADS-B In is the other side of the same coin. It is the technology that enables that beacon to be ‘seen’.
Standard in air traffic control centers, ADS-B In technology can also be fitted in aircraft, allowing them to receive the position, speed, heading and altitude of other aircraft around them. It updates every second and can display air traffic to a distance of up to 180 nautical miles out. For pilots, it provides a GPS-precision picture of the surrounding airspace on the flight deck in real time.
Essentially, ADS-B Out keeps you visible; ADS-B In keeps you informed.
Why it changes things
Traditional collision avoidance – TCAS – is reactive. It monitors nearby transponder signals and issues an alert when something gets too close. It is a last resort, identifying problems as they develop.
ADS-B In is proactive. Pilots aren't waiting for an alert. They can see the full picture continuously, plan ahead, and collaborate with air traffic control to manage airspace, rather than simply following instructions without the context behind them.
That shift – from reactive to proactive, from passive to collaborative – is what makes ADS-B In a significant development for the industry. It doesn't replace existing systems, but gives pilots the information they need to use existing systems more effectively.
What it looks like in practice
ACSS SafeRoute+ is the leading ADS-B In retrofit solution for commercial airlines. It installs as a software upgrade to existing TCAS, meaning no major hardware overhauls and no lengthy grounding. American Airlines completed a retrofit program across its entire A321 fleet, with aircraft down for three to four days at most during routine A-checks.
SafeRoute+ brings four core capabilities to the flight deck:
- Enhanced traffic awareness (AIRB): A continuous, detailed picture of surrounding aircraft up to 180 nautical miles, including flight ID, position, altitude, speed and direction. 84% of pilots in trials reported significantly improved situational awareness.
- Visual separation on approach (CAVS): Enables pilots to maintain precise spacing from the aircraft ahead during approach, even in reduced visibility. Reduces final approach time by up to 14% and cuts go-arounds.
- Interval management (IM): Reduces vectoring and increases airspace capacity by up to 23% on en-route segments.
- In-trail procedures (ITP): For oceanic routes without radar coverage, allowing aircraft to change altitude more efficiently to find better winds, delivering an average fuel saving of 670 lbs per transatlantic flight.
"When pilots are given better information, they make better decisions.”
American AirlinesSpokesperson
The proof
Between 2023 and 2024, the FAA ran a two-year operational evaluation at Dallas Fort Worth, one of the USA’s busiest airports. Installing SafeRoute+ across American Airlines’ A321 fleet, the results were unambiguous.
Spacing between arriving aircraft reduced by an average of 12 seconds. That translated to four to five additional landings per hour, per runway. In the first year alone, the trial recorded savings of 490,000 lbs of fuel, 700 metric tons of CO2 and $321,000 in operational costs. Across more than 2,000 operations, there were no separation-related safety incidents whatsoever.
An American Airlines spokesperson summed up the impact of ADS-B In technology neatly, saying: “When pilots are given better information, they make better decisions.”
Despite some initial caution, controllers at DFW were unequivocal that they wanted to keep using the technology once the trial was complete.
Likewise, pilots consistently supported continued use of ADS-B In, reporting situational awareness that was “much, much higher than before.”
| ADS-B Out | ADS-B In | |
| What it does | Broadcasts your position | Receives others’ positions |
| Mandatory in US? | Yes, since 2020 | Legislation advancing |
| Range | N/A | Up to 180 nautical miles |
| What it means for pilots | Allows you to be ‘seen’ | Enables you to ‘see’ |
The bottom line
ADS-B In doesn't ask pilots to do anything differently. It gives them what they have always needed: a complete, accurate, real-time picture of the airspace around them. The result is safer operations, more efficient arrivals and measurable commercial gains.
The technology is proven. The business case is clear. Plus, with the ALERT Act gaining momentum and the ROTOR Act having support, the compliance clock is ticking. Airlines can wait for legislation to land. Or they can act now, get ahead and start realizing the benefits of ADS-B In.
