How to Track Any Flight in Real Time with an ADS-B Radar Map

A plane crosses the sky above your street, low enough that you can read the tail, and you wonder where it is going. Ten years ago that question ended with a shrug. Now it takes about fifteen seconds and a browser tab. Public ADS-B radar maps show thousands of aircraft moving in real time, complete with altitude, speed, destination and the exact path they have flown so far.

What follows is a walkthrough for someone who has never used one of these maps before. We will find a specific aircraft, decode the numbers on its label, and follow a flight all the way from cruise to touchdown, including the points where the picture can mislead you.

What the map is actually showing you

Most commercial aircraft carry a transponder that broadcasts a short digital packet a couple of times per second. That packet contains an identity, a position, an altitude and a velocity, and it is transmitted openly on 1090 MHz. Anyone with a receiver within range can pick it up, and thousands of hobbyists and aviation enthusiasts do exactly that, feeding their local data into shared networks. The map you look at is those feeds stitched together.

Not every aircraft broadcasts ADS-B. Older airframes and some military traffic only emit the simpler Mode S signal, which carries no position. Networks estimate a position for those by comparing the arrival time of the same signal at several receivers in different places, a technique called multilateration. Such tracks are usually shown with a note that the position is estimated, and they are less precise than a direct broadcast.

The practical consequence is coverage. Around Europe and North America, receivers are dense and the map is close to seamless. Over oceans, deserts and large parts of Africa and South America, gaps open up, and some services fill them with satellite-based data while others simply show nothing. An empty patch of map does not mean empty sky. It often means nobody was listening.

Finding one specific aircraft

You can start from the search box or from the map itself. Both work, and the right choice depends on what you already know.

• By flight number. Use the code printed on a boarding pass, such as the two-letter airline code plus a number. This is the easiest route when you are tracking a friend or a relative.
• By registration. The tail number is painted on the aircraft itself: a short alphanumeric string beginning with a country prefix. Useful when you want to follow a particular airframe rather than a particular flight.
• By callsign. Air traffic control talks to the aircraft using a callsign, which usually resembles the flight number but not always. Position ferry flights and some charter services use something quite different.
• By clicking. Zoom in on the aircraft nearest to you and click the icon. If you can see it from your window, this is by far the fastest method.

If a flight refuses to appear, three explanations cover most cases. It may be outside receiver coverage, it may not yet have switched on its transponder before departure, or the operator may have asked to be filtered from public display. Business jets and government aircraft do this more often than you might expect.

Reading the live position

Every icon carries a label, and the label is where the real information lives. The first figure is altitude in feet. A short-haul jet in the cruise typically sits somewhere between 30,000 and 38,000 feet, and the figure changes as it climbs or descends. Next to the altitude you will often see a small arrow or a signed number giving the vertical rate in feet per minute. A rate of zero means level flight; a few thousand feet per minute down means the aircraft is on an arrival.

Speed is given in knots, and one knot is roughly 1.85 kilometres per hour. A cruising airliner shows something in the region of 450 to 500 knots over the ground. That word ground matters: the figure is affected by wind, so an aircraft flying west into a strong jet stream can show a considerably lower number than one flying east at the same altitude.

Track, heading and the direction of the icon

The nose of the icon shows the direction of travel, known as the track. It is almost never exactly the direction the aircraft is pointing, because crosswinds push it sideways. On the ground this distinction disappears, and near airports the icon will slide along taxiways at walking pace, which is a useful reminder that the aircraft has landed rather than vanished.

Codes worth knowing

The label may also show aircraft type, a four-digit squawk code, and the route string a crew has entered into the flight computer. Three squawk codes carry a fixed meaning everywhere: 7700 for a general emergency, 7600 for radio failure, 7500 for unlawful interference. Seeing one of these on the map is rare, and it is a strong signal that something unusual is happening, though crews do sometimes select them briefly by mistake while reprogramming.

Following the route from gate to gate

A flight page usually lists the departure and arrival airports, the scheduled times, and the aircraft type. The map draws two different things, and beginners often confuse them. The straight or gently curved line joining the two airports is a reference line, not a promise. The coloured trail behind the icon is what the aircraft has actually flown.

That trail is where the interesting details hide. Long-haul flights rarely follow the shortest path on the map, because winds aloft make a longer ground route cheaper in fuel. Eastbound transatlantic flights often bow north to ride the jet stream; westbound flights bow south to avoid it. Over land, the trail bends around restricted airspace, weather cells and busy terminal areas.

What the trail can tell you about the flight

Watch an arrival for ten minutes near a major airport and the trail starts to look like handwriting. Long, gentle S-curves at low altitude usually mean the aircraft is being vectored for spacing. A racetrack loop, repeated once or twice at the same spot, is a holding pattern, and it almost always means the airport is saturated or weather is disrupting the flow. A descent that suddenly reverses into a climb near the runway is a go-around.

Diversions show up the same way: an aircraft cruising steadily towards one airport, then turning away and heading somewhere else. Following the trail backwards is equally useful. If you have ever wondered why a flight was late, the answer is often visible as a long detour, a hold, or an unusually slow taxi across a large airport.

When the data looks wrong

These maps are a live approximation, not an official source, and a few artefacts are normal. Positions sometimes jump as an aircraft passes between receivers. Icons occasionally freeze for a few seconds during a handover. Some services deliberately delay certain data by several minutes for security or commercial reasons, so two sites showing the same flight may disagree slightly. Estimated positions, including multilateration tracks and ground vehicle labels, are less reliable than direct broadcasts. Treat the map as a helpful window on the sky, not as a certified record.

A five-minute routine to practise

1. Wait until you can hear or see an aircraft overhead, then open the map and zoom to your location.
2. Click the nearest icon and note its callsign and altitude.
3. Search that callsign to open the full flight page and check the destination.
4. Zoom out until you can see the whole route, then follow the trail backwards to the departure airport.
5. Zoom back in near the destination and keep the page open while the aircraft descends and lands.

Do that a few times and the labels stop looking like noise. You will start recognising the flow of arrivals into your local airport, the difference between a flight being vectored and one being held, and the small detours that explain a delayed landing. The map stops being a novelty and becomes a genuinely useful way to read the sky above you.

Photo: Phát Trương / Pexels