How does live aircraft tracking work, and what are its limitations?
Live aircraft tracking combines broadcasts from an aircraft—mainly ADS-B and Mode S—with ground receivers, satellite receivers, radar-derived feeds and flight-plan data. Tracking services merge these inputs into a map, but coverage, delay, filtering, receiver geometry, incorrect identifiers and aircraft that do not transmit usable data can make the picture incomplete or wrong.
For our Aviation & Real-World Flying readers, the key distinction is that “live” means the latest information available to the service. A public tracking map is a reconstructed view, not the complete surveillance picture seen by air traffic control.
How is a live aircraft position detected?
Most public tracking begins with ADS-B Out, a radio broadcast sent by the aircraft rather than a request from the tracking service. It can include the aircraft’s 24-bit ICAO address, entered flight identification, GNSS-derived position, altitude, ground speed, track and vertical rate.
Standard civil ADS-B messages are not encrypted, so receivers within radio line-of-sight can collect them and forward them over the internet. Most airline aircraft use 1090 MHz extended squitter; some light aircraft in the United States use 978 MHz UAT, which requires compatible receiving equipment.
| Tracking source | What it provides | Main limitation |
|---|---|---|
| ADS-B | Aircraft-reported position, altitude, velocity and identity | Requires compatible equipment, transmission and receiver coverage |
| Mode S with multilateration | A position calculated from the arrival times of transponder signals | Normally needs at least four synchronised receivers with good geometry |
| Satellite ADS-B | Coverage over oceans and sparsely populated regions | The public service must have access to the satellite feed; latency can vary |
| Radar or operational feeds | Surveillance positions and flight status from aviation systems | Access is restricted and differs by country and provider |
| Flight plans, schedules and registries | Route, operator, registration and airport labels | These are metadata, not proof of the aircraft’s position or actual route |
Mode S does not always provide a usable position directly. A network can instead use multilateration, measuring the tiny differences in a transmission’s arrival time at several receivers. Poor receiver spacing or an aircraft outside the network’s perimeter can produce an inaccurate fix or no fix at all.
The tracker then matches the broadcast address and flight identification against registry, schedule and flight-plan records. This matching process is why a map can show the correct position but the wrong registration, route or commercial flight number.
Is live aircraft tracking really real time?
Live tracking is usually delayed by at least the time needed to receive, upload, process and display each message. A good terrestrial ADS-B feed may appear within seconds, while satellite, partner or deliberately delayed feeds can take longer.
Map applications also interpolate between reports so icons move smoothly. If reception stops, some systems briefly extrapolate the aircraft’s course rather than freezing it immediately. A moving symbol therefore does not guarantee that a fresh position has just arrived; the report age and any “estimated” indicator matter more.
Why do aircraft disappear from tracking maps?
An aircraft usually disappears because the service has lost usable data, not because something has happened to the flight. Common causes include:
- Radio horizon: ADS-B and Mode S are line-of-sight signals. Mountains, buildings and Earth’s curvature block them, especially as an aircraft descends.
- Sparse receiver coverage: Remote regions, low altitudes and some coastlines may have too few ground receivers. Satellite reception only helps when the tracking service receives that feed.
- Poor multilateration geometry: Several receivers may hear a Mode S transmission without being positioned well enough to calculate an accurate fix.
- Equipment differences: Some aircraft are not required to carry ADS-B in the airspace where they operate, or they use another electronic conspicuity system that the tracker does not ingest.
- Operational or technical issues: A transponder can be incorrectly configured, unavailable or legitimately operated under procedures that do not produce a public track.
- Feed failure: The aircraft may still be transmitting while a volunteer receiver, internet connection or processing service is offline.
Reception near airports is often less complete than reception at cruising altitude. An airliner at high level may be visible to receivers hundreds of kilometres apart, then vanish behind terrain or airport buildings during its final descent or while taxiing.
Can every aircraft be tracked?
No public tracking service can display every aircraft. Equipment mandates vary by aircraft, altitude, airspace and country, while military, government, police and other sensitive operations may be exempt, use different surveillance arrangements or be filtered from public displays.
An owner-requested or security-related display block does not necessarily hide the aircraft from air traffic control or from a suitably equipped local receiver. Conversely, primary radar can detect an aircraft without receiving a transponder reply, but that complete radar picture is rarely available to public tracking applications.
What live tracking errors should you expect?
The most common errors concern identity, altitude and stale positions rather than the basic concept of tracking. A mistake we see constantly is treating every label on the map as information broadcast directly by the aircraft.
- Wrong callsign or flight number: The flight identification is entered into the aircraft’s systems and can be mistyped. An airline callsign may also differ from the passenger-facing flight number, particularly on codeshares.
- Wrong registration or aircraft type: Registry databases can lag behind ownership changes, while an incorrectly programmed ICAO address can associate a position with another airframe.
- Incorrect route: Origin and destination are often matched from schedules or flight plans. Diversions, positioning flights and last-minute aircraft swaps can defeat that matching.
- Altitude differences: Tracking displays commonly use broadcast barometric altitude, while a cockpit, simulator or another source may show pressure-corrected or GNSS altitude. These values are not interchangeable.
- Speed differences: ADS-B commonly provides ground speed. It will not match indicated airspeed, and wind can create a large difference between ground speed and true airspeed.
- Position jumps: Weak multilateration geometry, bad source data, GNSS interference or spoofing can place an aircraft away from its real position. Processing filters reject many bad reports, but not all of them.
- Ghost or duplicate tracks: A service can briefly fail to merge reports from different feeds, or it may display schedule-based information after the corresponding live track has disappeared.
Why does live traffic differ from a flight simulator?
Flight simulators add a translation layer between tracking data and the aircraft shown in the virtual world. The simulator must create an AI object, choose an installed model and livery, interpret the callsign, manage ground movement and discard traffic beyond its own limits.
Some products use near-live positional feeds, while others generate AI traffic from real-world schedules. We explain that distinction in our comparison of ADS-B-based and schedule-based simulator traffic. The extra conversion step is also visible in an FSX utility that turns received aircraft information into AI traffic and flight plans.
Even two services using related source data may refresh at different times or apply different privacy and validation rules. That is one reason live ATC audio may not match simulator traffic: an aircraft can be delayed, filtered, model-matched under another callsign or absent from the simulator entirely.
- Choose live positional traffic when seeing a particular real flight in approximately the right place matters most.
- Choose schedule-based traffic when consistent airport activity and plausible airline routes matter more than exact live positions.
- Choose offline AI traffic for repeatable scenarios and operation without an online data feed.
Can live aircraft tracking be relied on?
Live aircraft tracking is useful for general awareness, flight following and simulation, but it is not an approved tool for navigation, separation, accident assessment or emergency decisions. Missing data does not prove an aircraft has landed or encountered trouble, and a displayed position is not guaranteed to be complete or exact.
Check the age and source of the report, distinguish reported positions from estimates, and treat route and identity labels as database matches rather than absolute facts. For operational decisions, use information supplied through the appropriate airport, aircraft operator or air traffic authority.