How Flightradar24 Tracks Flights Using Open Data: ADS‑B, MLAT and More

Flightradar24 started as a little‑known hobby project and suddenly went viral, attracting hundreds of thousands of users who wanted to track flights in real time.

The service displays aircraft on a map, allowing users to select a plane and view detailed flight information and its live trajectory.

Using Open Data to Track Flights

In simple terms, Flightradar24 relies on open data sources to achieve flight tracking.

According to its official site, the platform combines multiple data sources, including ADS‑B, MLAT, radar data, as well as airline and airport schedules and flight‑status information.

ADS‑B

ADS‑B (Automatic Dependent Surveillance‑Broadcast) is the primary technology Flightradar24 uses to receive flight information.

The process works as follows:

Aircraft determine their position via satellite navigation.

The onboard ADS‑B transponder periodically broadcasts this position.

Flightradar24’s ground receivers pick up the signals.

The data are then synchronized to the website and app.

Beyond ground control and tracking sites, ADS‑B also provides pilots with useful data such as altitude, heading, speed, conflict alerts and route waypoints, offering faster updates, higher accuracy, richer information, and lower installation costs compared with traditional radar.

Most aircraft worldwide are now required to be equipped with ADS‑B, and Flightradar24 operates the world’s largest ADS‑B network with over 30,000 ground receivers.

MLAT

When an aircraft lacks an ADS‑B transponder, Flightradar24 can still locate it using MLAT (Multilateration), which calculates position based on the time‑difference of arrival (TDOA) of signals from the aircraft’s older transponder received by multiple ground stations.

MLAT requires at least four receiving stations to triangulate the aircraft’s location.

Flightradar24 also incorporates satellite data, North American radar feeds, and the Open Glider Network (OGN) for additional coverage.

The platform offers fun features such as a “3D view” button that renders aircraft in three‑dimensional space.

From a Hobby Project to the Most Popular Flight‑Tracking App

Today, Flightradar24 is one of the most downloaded travel apps on both the Apple App Store and Google Play, with over 40 million downloads.

It began as a hobby by Swedish developers Mikael Robertsson and Olov Lindberg, who initially set up small receivers on their roof to monitor flights over Stockholm.

In 2006 they added flight‑tracking to a ticket‑price comparison site, attracting aviation enthusiasts who contributed their own receivers.

By 2009 they opened the network to anyone with an ADS‑B receiver, allowing global data contributions.

The service now provides comprehensive flight details—including origin, destination, call sign, position, altitude, speed, heading, and even cockpit settings—and is used by air traffic controllers and professionals.

Major events such as the 2010 Icelandic volcano eruption and the 2014 MH17 crash drove massive traffic spikes, prompting commercial expansion and a global app rollout.

Regulatory mandates, such as the FAA requirement for all aircraft to carry ADS‑B transmitters by 2020, have further boosted adoption.

Flightradar24 now tracks over 180 000 flights daily, with more than 2 million active users.

One More Thing

To protect privacy, Flightradar24 filters certain data, though occasional leaks have exposed routes of high‑profile flights.

Other similar services include ADS‑B Exchange, FlightAware, OpenSky Network, Radarbox24, and PlaneFinder, each offering varying levels of data openness.