How Does Live Flight Tracking Work? ADS-B Explained
If you've ever used a flight tracking app, or watched a display like NearestPlane show a plane passing overhead in real time, you've probably wondered how that data actually gets to your screen seconds after it happens. The short answer is a system called ADS-B. Here's the longer, more useful answer.
The basic idea: planes already broadcast their own position
Most aircraft flying today carry a transponder that broadcasts ADS-B (Automatic Dependent Surveillance–Broadcast) data automatically, roughly once a second. This broadcast includes the aircraft's identity, exact GPS position, altitude, speed, and heading. It's not a request-response system — the aircraft just broadcasts it, constantly, to anyone listening.
Originally this was built for air traffic control, so controllers could track aircraft more precisely than older radar allowed. But because it's an open broadcast, not an encrypted or restricted one, anyone with the right receiver can pick it up too.
Who's actually listening
This is the part people usually don't realise: the flight tracking data you see on an app or display doesn't come from the airline, or from a single government system. It comes from a global network of thousands of independent ADS-B receivers — small antennas run by hobbyists, aviation enthusiasts, and companies, often on rooftops and windowsills, all feeding their received signals into shared networks.
Services aggregate these thousands of feeds, cross-reference them, and produce the live map or live data you see. That's also why coverage is generally excellent near cities and populated areas (more receivers) and patchier over oceans and very remote regions (fewer receivers) — although satellite-based ADS-B coverage has closed much of that gap in recent years.
Why it updates every 30 seconds (not instantly)
Individual ADS-B broadcasts happen roughly once a second, but most consumer tracking products — apps and displays alike — refresh their displayed data every 15 to 30 seconds rather than continuously. This is partly to manage data volume sensibly, and partly because for a person watching a screen, half-second precision doesn't add anything useful; a smooth 30-second refresh reads as live without needing constant redraws.
How this applies to something like NearestPlane
NearestPlane works exactly on this principle: it's a small WiFi-connected device that pulls live ADS-B data for your area, filters it down to the nearest aircraft (or a specific flight you've asked it to track), and displays it on an LED matrix — airline, route, altitude, speed — refreshed every 30 seconds. There's no subscription because the underlying ADS-B data is fundamentally an open broadcast network, not a paid feed the display owner has to keep renewing.
If you're curious what this looks like on your own shelf, rather than in an app, see how NearestPlane works →
Quick answers
Is ADS-B data free to access?The raw broadcasts are open and unencrypted, but most consumer-facing tracking products (apps, displays, and websites) rely on aggregated feeds from networks that combine thousands of receivers — accessing those aggregated feeds is usually how the cost structure works, even though the underlying broadcasts themselves are public.
Does every aircraft broadcast ADS-B?The large majority of commercial aircraft do, and it's now mandated in most major airspaces. Some smaller general aviation aircraft, older military aircraft, and aircraft deliberately operating without transponders may not appear on public trackers.
Why do some flights briefly disappear from a tracker?Usually a gap in receiver coverage (over water or very remote terrain) rather than the aircraft actually going dark — this is far less common than it used to be as coverage has expanded.
Curious what live ADS-B data looks like as a physical display rather than an app? See NearestPlane →, read our comparison of the best flight trackers in 2026, or find out what's flying above you right now.