Aircraft broadcast their own position. That is the whole trick behind modern flight tracking: a transponder computes where the aircraft is from satellite navigation and announces it, in the clear, roughly twice a second, to anyone within radio range. There is no encryption and no addressee. A cheap antenna and a software-defined radio in a suburban window can decode airliners two hundred nautical miles away.
So if the signal is public, why do trackers disagree about what is in the sky?
Two very different pipelines
Because "what the aircraft broadcast" and "what a tracker shows you" are separated by a supply chain, and there are two common ways to build it.
The first is to take a government data feed. In the United States the FAA distributes flight and surveillance data to industry through its System Wide Information Management programme; other countries have equivalents. It is convenient, wide-area, and already cleaned up. It is also filtered before it leaves, because the agency operates programmes that let operators ask to be left out of it.
The second is to receive the radio signal directly. A volunteer runs a receiver (often a small computer and an inexpensive radio dongle) pointed at 1090 MHz, and forwards what it decodes to a shared network. Thousands of those receivers aggregated together produce a map that came from the air rather than from an agency. That is what airplanes.live is, and it is where this app's aircraft data comes from.
The distinction matters because the filtering happens in the first pipeline, not in the second. A tracker built on an official feed inherits every exclusion that feed applies. A tracker built on volunteer receivers inherits none of them, and has to decide for itself whether to re-impose any. We don't.
The three things that usually disappear
LADD: aircraft withheld from the public feed
The FAA runs a programme called Limiting Aircraft Data Displayed, or LADD. It is the successor to what used to be called BARR, the Block Aircraft Registration Request. An aircraft's owner or operator can ask the FAA to withhold that aircraft's data from public distribution. Corporate flight departments, sports teams and private owners use it routinely.
The critical detail, which is very widely misunderstood: LADD does not change what the aircraft transmits. It is a request about the agency's redistribution of data. The aircraft's transponder continues to broadcast its position, its ICAO address and its callsign to every receiver in line of sight, exactly as before. Nothing is switched off, nothing is obscured. A receiver on a rooftop cannot tell a LADD aircraft from any other, because there is nothing in the signal to tell.
PIA: a temporary, unlisted identity
The FAA also operates the Privacy ICAO Address programme. Every ADS-B-equipped aircraft transmits a 24-bit ICAO address, its hex code. That address normally maps one-to-one to a registration in the public civil aircraft registry. Under PIA, an eligible US-registered aircraft operating in domestic airspace can be assigned an alternate, temporary address that is not the one listed against it in the registry, and typically flies under a call sign issued through a third-party provider rather than its tail number.
This one genuinely does change the broadcast, but not in the way people assume. The aircraft is still there, still transmitting position twice a second, still perfectly visible to any receiver. What breaks is the lookup: the hex code no longer resolves to a name. So a PIA aircraft appears on our map as an aircraft, because it is one. It simply appears without an owner attached, which is the point of the programme and is a result we are entirely comfortable with.
Military and other "sensitive" traffic
Many military aircraft broadcast ADS-B like everyone else: training flights, transports, tankers, air-refuelling tracks, search and rescue. Some do not, and crews can switch a transponder off when the mission calls for it, in which case no tracker on earth will show them. But of the ones that are broadcasting, it is common for consumer trackers to suppress the display as a matter of policy.
We show them. Not as a stunt: a tanker orbiting a refuelling track, a coast guard aircraft flying a search pattern, or a heavy transport in and out of a local field is often the single most interesting thing in the sky, and it is announcing itself publicly to anyone with an antenna. Hiding it from the map does not hide it from the air.
What we do not do
Unfiltered means we do not delete targets that the network received. It does not mean we try to defeat anyone's privacy measures. We do not attempt to correlate Privacy ICAO Addresses back to registrations, we do not publish owner identities the registry does not, and the terms of use prohibit using the app to harass or surveil individuals. The distinction is between not removing a public broadcast and actively unmasking someone. We do the first and not the second.
What unfiltered does not mean
It does not mean complete. A map built from volunteer receivers is honest about a real limitation: no receiver, no aircraft. Coverage is excellent over populated areas with an active feeder community and thin everywhere else. Being unfiltered is a statement about what we remove, not a promise about what we receive.
Aircraft go missing for reasons that have nothing to do with policy:
| Reason | What is happening |
|---|---|
| No ADS-B equipment | Older general aviation aircraft, gliders, balloons and aircraft without electrical systems are not all required to carry ADS-B Out and many do not. |
| Mode A/C only | A legacy transponder replies to radar with a squawk code and altitude but carries no unique address and no position. There is nothing for a ground receiver to attach a track to. |
| Below the radio horizon | 1090 MHz is line of sight. Low-level traffic disappears behind terrain and the curvature of the earth long before high-level traffic does. |
| No receivers nearby | Oceans, deserts and sparsely populated regions have few volunteers. Mid-ocean gaps are gaps in the network, not in the aircraft. |
| Multilateration falls short | Aircraft with Mode S but no ADS-B position can sometimes be located by multilateration, which needs four or more receivers with synchronised clocks hearing the same transmission with good geometry. Where that isn't available, they stay unplotted. |
| The transponder is off | Nothing transmitted, nothing received. This is the honest end of the story for aircraft that genuinely do not want to be seen. |
There is also a category worth naming: an aircraft whose position is wrong rather than absent. ADS-B is "dependent". It repeats what the aircraft's own navigation system believes. Where GNSS is being jammed or spoofed, aircraft broadcast confidently incorrect positions, and the tracker faithfully draws them. We map that too, at /jamming.
Why this is worth caring about
A flight tracker that quietly removes categories of aircraft is not showing you the sky. It is showing you an edited version of the sky, with the edits unmarked, and the things most likely to be edited out are frequently the things most worth seeing. Somebody watching a wildfire, following a medical transport, or simply trying to identify the loud aircraft that just went over the house is best served by a map that answers the question rather than one that has been pre-approved.
None of this requires special access. It requires not throwing data away.
