How Live Flight Tracking Works

Every few seconds, your flight is shouting its location to anyone listening. Most airliners carry an ADS-B transponder — a small radio that broadcasts the aircraft's GPS position, altitude, speed, heading, and callsign on 1090 MHz, roughly twice a second. The signal is unencrypted by design: it exists so air-traffic control and nearby aircraft can see each other, and anyone with an inexpensive antenna can receive it.

ADS-B stands for Automatic Dependent Surveillance–Broadcast. Automatic because it transmits without pilot input, dependent because it relies on the aircraft's own GPS, and broadcast because it goes out to everyone in range — typically 100 to 250 miles at cruising altitude. That open broadcast is the entire reason live flight tracking exists.

Each burst — called an extended squitter — carries a compact packet: a unique 24-bit aircraft address, the callsign, latitude and longitude, barometric altitude, ground speed, heading, and vertical rate (climbing or descending, and how fast). Newer transponders add extras like the selected autopilot altitude, which is why some trackers can show you the altitude a plane is cleared to before it gets there.

What's not in the signal is just as telling: no passenger count, no cargo manifest, no flight plan. Origin and destination on your tracker come from schedule databases matched to the callsign, not from the aircraft itself — which is why a diverted flight sometimes shows a destination it never reaches.

The magic ingredient is volunteers. Thousands of aviation enthusiasts run inexpensive ADS-B receivers — often a small antenna on a roof feeding a computer — and share the data with aggregator networks. Each receiver covers a bubble of sky; stitch thousands of bubbles together and you get near-global coverage over land.

Older transponders don't broadcast GPS positions, but they still reply to radar interrogations — and networks locate those aircraft with multilateration (MLAT), timing the same reply at multiple receivers to triangulate a position. It's less precise than ADS-B and needs several receivers in range, which is why MLAT coverage is patchier.

Over oceans and remote regions, where no volunteer's antenna can reach, satellite-based ADS-B receivers fill the gaps. The result is a tracking map that can follow a flight from gate to gate — with the caveat that coverage thins exactly where you'd expect: mid-ocean, polar routes, and sparsely populated land.

A good flight map turns raw packets into a picture: each aircraft as a marker with a trailing path, often colored by altitude — warm tones low near the ground, cool tones up high. Click any plane and you get the telemetry: callsign, aircraft type, registration, speed, altitude, heading, vertical rate, and the origin-destination pair from the schedule database.

Learn to read the trails. A long straight trail at constant altitude is cruise; a descending corkscrew is a holding pattern; a sudden break in the trail usually means the aircraft left receiver coverage, not that it vanished. Zoom into a busy hub at arrival rush and you can watch controllers sequence the flow — spacing, S-turns for delay, and the final lineup onto the runway.

Altitude color is the quickest read on the map: warm colors mean low and slow — departures climbing out or arrivals on final — while cool colors mean high and fast at cruise. A flight that shifts color mid-trail is starting its descent, which is why the color change over a hub's arrival corridor lines up with the published approach fixes.

Not everything flies visible. Some operators request privacy blocking, so their aircraft appear with limited or no identification. Military and sensitive government flights often don't broadcast at all, or fly with transponders off in certain airspace. And because the system is unencrypted, the data can technically be spoofed — researchers have demonstrated ghost aircraft, though it remains rare in practice.

Coverage has edges, too. Low-altitude flights in rural areas may drop in and out of receiver range, and some aggregators deliberately delay certain data by a few minutes. A missing aircraft on the map is usually a coverage story, not a mystery.

The best way to understand ADS-B is to watch it. WorldEye's live flight tracker plots aircraft on the free 3D globe in real time — no account, no signup. New to flight tracking? The beginner's guide covers the basics first. Pick a hub you know, find an inbound flight, and follow its trail all the way to the runway — then check the airport's cameras for the ground view.

Aviation is one of the purest examples of open data at planetary scale: millions of broadcasts a day, collected by volunteers, visible to everyone. Once you see the sky as a live system, the departure board never looks the same. And once you've watched a holding pattern draw itself over your home airport during a storm, you'll never wonder why your flight is delayed for weather again.

Curious about the camera layer, offline feeds, or how the map handles data gaps? The FAQ has answers, and about WorldEye explains what the platform is building toward.