How Flight Tracking Works: ADS-B Explained Simply
Quick answer
Live flight tracking mostly works thanks to ADS-B: each aircraft figures out its own position from GPS and broadcasts it — with altitude, speed and identity — several times a second. A network of ground receivers and satellites picks up those signals and a tracker plots them on a map. When a flight seems to disappear, it is usually a coverage gap or a privacy setting, not a lost plane.
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The one idea behind modern tracking: ADS-B
ADS-B stands for Automatic Dependent Surveillance-Broadcast. The name sounds intimidating, but the pieces are simple. It is automatic because the aircraft sends the data on its own with no request. It is dependent because it depends on the plane's own navigation system, mainly GPS. It is surveillance because it is used to watch traffic, and broadcast because the signal goes out to anyone in range who can receive it.
In practice, the aircraft's transponder transmits a small burst of data roughly twice a second. That burst includes where it is, how high it is, how fast it is moving and a unique identifier. Any receiver nearby can decode it — that is the whole trick.
From aircraft to your screen, step by step
| Step | What happens |
|---|---|
| 1. Position | The aircraft's GPS calculates its exact location |
| 2. Broadcast | The transponder sends position, altitude, speed and ID (ADS-B Out) |
| 3. Reception | Ground receivers and satellites pick up the signal |
| 4. Processing | Data is combined, cleaned and matched to flight schedules |
| 5. Display | A tracker plots the plane on a live map for you to follow |
What the transponder actually says
A transponder is a small radio on the aircraft that responds to and sends signals. With ADS-B "Out," it continuously announces the flight's details. Older secondary radar asks a plane to reply; ADS-B flips this around so the plane simply keeps talking. That constant chatter is why trackers can update so smoothly.
Ground receivers and satellites
Over land, thousands of inexpensive receivers — many run by aviation enthusiasts — listen for these broadcasts and feed the data into networks. Over oceans and remote regions where no one can place a receiver, satellites equipped to catch ADS-B fill much of the gap. Together they build near-global coverage, though the quality still varies by region.
Why flights sometimes vanish from the map
- Coverage gaps: mid-ocean or over sparse terrain, terrestrial receivers cannot hear the plane and satellite updates may lag.
- Privacy settings: some operators request that a tail number be limited or hidden from public feeds.
- Older aircraft: a plane without ADS-B Out is harder or impossible to show live.
- Signal dropouts: a brief interruption can make a track pause before it reappears.
None of these mean the aircraft is in trouble — it simply is not being heard clearly at that moment.
How to read a flight tracker
Most trackers show the plane's icon, its route line, current altitude and ground speed, plus scheduled and estimated times. A climbing altitude and rising speed after departure is normal; a holding pattern near the destination usually means the airport is busy. If you are meeting someone, watching the inbound aircraft is often the fastest way to know whether their flight will be late.
Frequently asked questions
What is ADS-B in simple terms?
It is a system where the aircraft works out its own position from GPS and automatically broadcasts it, along with altitude, speed and identity, several times a second. Receivers on the ground and in space pick that up and trackers map it.
Why do some flights disappear from the tracker?
Ocean and remote-area coverage gaps, privacy-limited tail numbers, older aircraft, or a brief signal dropout can all cause it. Satellites help over water but not always instantly.
Is the data delayed?
Ground ADS-B is usually within seconds of real time. Some feeds add a short delay, and a few flights or regions show more lag or nothing at all.
Can I track any flight?
Most commercial flights, yes, because their aircraft broadcast ADS-B within receiver range. Some private or privacy-limited flights may be hidden.
The bottom line
Flight tracking looks like magic but rests on one clean idea: planes announce where they are, and a global web of receivers listens. Understanding ADS-B makes the map easier to read — and easier to trust when a flight briefly drops off it. Follow a live flight on ScanFlyGo, then compare fares for your next trip or browse popular routes.
Some links on ScanFlyGo are affiliate links — we may earn a commission at no extra cost to you. Tracking coverage and timing vary by region and data source.