The Privacy ICAO Address, Why ADS-B Out Broadcasts Your Tail Number in the Clear, and the Anonymity Program the FAA Built to Give It Back

Since January 2020, nearly every aircraft in controlled U.S. airspace has been required to broadcast ADS-B Out - an unencrypted radio signal that announces its GPS position, altitude, speed, and a unique identifier once per second, in a public format anyone can decode. That identifier maps directly to your tail number, and your tail number maps to your name and address in the public FAA registry. The Privacy ICAO Address (PIA) program and the Limiting Aircraft Data Displayed (LADD) list are the FAA’s two tools for bolting privacy back onto a system that was designed to be open.

What Is ADS-B and Why Does Every Aircraft Broadcast It?

ADS-B stands for Automatic Dependent Surveillance–Broadcast, and the name explains itself once you break it apart. It’s automatic because it runs without a controller requesting it or a pilot pushing a button. It’s dependent because it relies on the aircraft knowing its own position from GPS. It’s surveillance because the purpose is watching traffic. And it’s broadcast because that’s literally what it does - it transmits.

Traditional radar works the opposite way. A ground dish sweeps around, sends a pulse, and waits for the echo, updating a fuzzy position every few seconds. Radar is slow, expensive, and blind over oceans and mountains.

ADS-B flips the model. Instead of the ground locating the aircraft, the aircraft locates itself via GPS and announces that position to everyone. The requirement lives in Federal Aviation Regulation 91.225. If you fly into Class B, Class C, above 10,000 feet, or inside the Mode C veil around major airports, your aircraft is broadcasting ADS-B Out right now.

Is the ADS-B Signal Encrypted?

No. The ADS-B Out signal is not encrypted, scrambled, or protected in any way. It is a plain radio transmission on a published frequency, formatted in a public standard that anyone can look up.

That openness was a deliberate design choice, and it produced real safety gains. Because position comes straight from GPS and updates every second, controllers get a picture faster and sharper than radar ever delivered - including over the Gulf, the Alaskan mountains, and other places radar never reached.

Pilots benefit too. With ADS-B In, the receiving half of the system, the cockpit gets free traffic displays and, on the 978 MHz frequency, free weather - radar imagery, METARs, and winds piped up from the ground. A generation ago, that capability would have cost a fortune in a small general aviation aircraft.

Who Can Track an Aircraft Using ADS-B?

Anyone with roughly a $20 software-defined radio dongle and a laptop can pull aircraft positions out of the sky. The signal doesn’t check credentials - physics delivers it to every receiver in range equally.

Over the past decade, an entire ecosystem grew around capturing these broadcasts. Sites like FlightAware, Flightradar24, and ADS-B Exchange are, at their core, networks of thousands of volunteers running cheap receivers on rooftops and feeding what they catch into a central map. Open one in a browser and you can watch nearly every aircraft in the sky, live, for free.

The privacy implications scale with who you are. A business jet’s competitors can watch which cities it visits before a merger. A public figure’s aircraft can be tracked to a private ranch. High-profile tracking accounts - including one that relentlessly followed a certain billionaire’s Gulfstream - turned this capability into international news. The aircraft is simply telling the truth about its location, out loud, every second, and someone built a website to write it all down.

How Does a Tail Number Get Exposed?

Every ADS-B aircraft broadcasts a unique ICAO address - named for the International Civil Aviation Organization. It’s a 24-bit number (a string of 24 ones and zeros) assigned to a specific airframe at registration.

In the United States, that ICAO address maps directly and publicly to the aircraft’s tail number, or N-number. The mapping is published in the FAA registry, which anyone can download. The chain is short and unbroken:

• The transponder broadcasts the ICAO address.
• The address maps to the N-number.
• The N-number maps, in the same public registry, to the owner’s name and address.

One broadcast, and a stranger can walk from a blip on a map to your front door. That’s the surveillance problem in a single sentence: a safety system that works by telling everyone who you are.

What Is the Privacy ICAO Address (PIA) Program?

The Privacy ICAO Address program, or PIA, lets an eligible aircraft broadcast an alternate, temporary ICAO address instead of the permanent one tied to its tail number. The temporary address is not listed in the public registry. The aircraft still broadcasts ADS-B Out, still appears for controllers, and still keeps everyone safely separated - but the identifier going out over the air no longer leads a stranger straight to a name.

It has real limits, and it’s worth being honest about them:

• Frequency limitation. PIA works only on the 1090 MHz frequency (1090ES). It does not work on the 978 MHz UAT system that many light aircraft use, so a large slice of general aviation can’t use it as designed.
• Not invisible to authorities. You request participation through a third-party service provider that works with the FAA, and the system manages the alternate address. Controllers and the FAA still know who you are - this was never about hiding from air traffic control.
• Correlation defeats it. A temporary anonymous number stays anonymous only until someone connects it to a pattern. If an aircraft always departs the same private hangar, a determined tracker can watch that hangar, note which mystery address lifts off, and connect the dots. You aren’t encrypting anything - you’re just making the label harder to read.

What Is LADD and How Is It Different From PIA?

Limiting Aircraft Data Displayed (LADD) - formerly the Block Aircraft Registration Request (BARR), which older pilots still call “the block list” - is a data-side tool rather than a radio-side one. It asks the FAA and the flight-tracking companies that agree to honor it not to publish an aircraft’s data to the public.

The gap is built into how it works. LADD is a request - a gentlemen’s agreement about what gets displayed. It does nothing to the radio signal itself. The aircraft is still broadcasting in the clear, once a second, for anyone with a $20 receiver. A tracking site that chooses not to honor the list - and some pointedly do not - can still show you.

In short: LADD hides you from the polite trackers. PIA tries to hide you from the impolite ones. Neither one turns off the beacon.

The Bigger Picture: A System That Is Both Marvel and Megaphone

ADS-B is fast, cheap, accurate, and open. The openness is a feature - it’s what made the system affordable and what put free traffic and weather into a Cessna. The openness is also a bug, because it means privacy has to be added afterward, imperfectly, instead of designed in from the start.

The same unencrypted, unauthenticated quality raises a security question beyond privacy: in theory, the signal can be spoofed, letting someone broadcast a ghost aircraft that doesn’t exist. The industry is aware of this, and there’s ongoing work to validate ADS-B targets against other sources - including multilateration, which cross-checks a signal by measuring how long it takes to reach several ground stations.

The practical takeaway for any pilot, whether you fly a two-seat trainer or a business jet: when you flip the transponder to ALT and roll onto the runway, you aren’t just squawking a code for the controller. You’re announcing yourself to the entire radio horizon, and not everything listening is the FAA. That’s not a reason for fear - it’s a reason to understand your own aircraft. And if you have a genuine need for privacy, know exactly what these tools do and don’t do, and don’t mistake a harder-to-read label for a locked door.

Key Takeaways

• ADS-B Out has been mandatory since January 2020 under FAR 91.225 for most U.S. controlled airspace, broadcasting position, altitude, and identity once per second.
• The signal is unencrypted, and the broadcast 24-bit ICAO address maps through the public FAA registry to a tail number, owner name, and address.
• Anyone with a ~$20 receiver can track aircraft; sites like FlightAware, Flightradar24, and ADS-B Exchange aggregate these broadcasts for free.
• PIA assigns a temporary, unlisted ICAO address on the 1090 MHz frequency only - it does not work on 978 MHz UAT, and controllers still know who you are.
• LADD only asks tracking sites to hide your data; it does nothing to the radio signal, and not every site honors it.