How FlightRadar24 became the world’s largest aviation information network—run by volunteers

Every commercial aircraft flying today broadcasts its position, altitude, speed, and identity continuously on an unencrypted public radio frequency. 

This was not an accident. It was a deliberate design decision made by the engineers who developed ADS-B — Automatic Dependent Surveillance-Broadcast — as the successor to radar-based air traffic control. Radar requires expensive ground infrastructure. ADS-B requires only a transponder on the aircraft and a receiver on the ground tuned to 1090 MHz. The signal is public because making it public makes it more useful for air traffic control: any receiver anywhere can hear it, which means coverage extends wherever receivers exist.

The FAA and the European Union Aviation Safety Agency both mandated ADS-B equipment on commercial aircraft by January 2020. When the mandate took effect, the global commercial fleet was broadcasting continuously on a public frequency. What the regulators did not fully anticipate was the $35 Raspberry Pi, the $20 software-defined radio dongle, and a global community of aviation enthusiasts willing to point antennas at the sky and share what they heard. ADS-B did not become a public information system because anyone planned it. It became one because the signal was always public, and eventually, the tools required to receive it became cheap enough that anyone could receive it.

TWO SWEDES WITH A ROOFTOP ANTENNA

Open FlightRadar24 on your phone, and you will see the sky above you represented in real time: each aircraft shown as a small icon, its flight number, altitude, speed, and origin visible when you tap it. The display is so immediate, so complete, and so apparently authoritative that it is easy to mistake it for an official system — for something operated by aviation authorities, airlines, or governments.

It is not. FlightRadar24 was founded in 2006 by Fredrik Lindahl and Olov Lindqvist, two Swedish software developers with no professional aviation background, who noticed that ADS-B signals from aircraft flying above Stockholm were publicly receivable by anyone with the right hardware. They built a receiver. Then another. Then they opened the network to outside contributors in 2009 and asked strangers on the internet to build more.

They did not know, at the time, that they were building an accountability mechanism for private jets, a transparency tool for investigative journalists, or the most complete civilian picture of global aviation available outside government systems. They were listening to what the sky was already saying. 

By 2026, that network will have grown to more than 55,000 receivers across all seven continents. Of those, approximately 7,000 were supplied by FlightRadar24. The remaining 48,000 were built or sourced independently by the people running them.

Those approximately 48,000 receivers have human beings behind them. A retired engineer in Edmonton, Alberta, has an antenna mounted on a 20-foot mast above his garage that tracks aircraft up to 200 nautical miles away. A hobbyist in Prague attached his antenna to an ash tree in his garden. An aviation enthusiast in Milan mounted his on a rooftop outside the city. FlightRadar24 sends between 30 and 50 complete receiver kits — antenna, cables, receiver unit — to new volunteer hosts every week, at no charge, in exchange for the data those hosts feed back to the network. None of them is paid. Individually, they are hobbyists. Collectively, they operate one of the world’s largest distributed sensing networks.

HOW IT WORKS

The technology at the foundation is ADS-B (Automatic Dependent Surveillance-Broadcast). Every commercial aircraft in regulated airspace carries a transponder that continuously broadcasts its position, altitude, speed, heading, and flight number — automatically, without pilot input, on a public frequency. ADS-B was developed to replace radar, which requires expensive ground infrastructure and has blind spots over oceans and mountains. ADS-B requires only a receiver tuned to 1090 MHz. Any receiver within approximately 400 kilometers can hear it. The broadcast is unencrypted. FlightRadar24 did not hack the aviation system. It listened to what the system was already saying.

FlightRadar24’s 55,000 receivers do exactly this, continuously, across all seven continents. Each receiver sends data to servers where it is aggregated, deduplicated, and displayed on the map. Over oceans and polar regions, ground-based receivers historically lost aircraft beyond radio range. In February 2026, FlightRadar24 integrated data from Aireon’s space-based ADS-B network aboard the Iridium satellite constellation, extending near-global coverage to oceanic and polar routes. The flight from Dubai to New York, which previously disappeared from the map for hours over the Atlantic, is now trackable from departure to landing.

The broadcast is unencrypted. It is, by design, public. The sky above any city is full of aircraft announcing their position, altitude, and identity to anyone with a receiver tuned to 1090 MHz. Most people do not know this. FlightRadar24 was built by people who did.

WHAT THE DATA HAS BEEN USED FOR

FlightRadar24 describes itself as a flight tracking service. It has become, through the public accessibility of its data, something closer to a global accountability mechanism for private and government aviation.

Journalists have used FlightRadar24 to track private jets belonging to oligarchs and public figures, identifying movements that contradicted official statements. The account @ElonJet produced a continuous record of a billionaire’s movements using only publicly available ADS-B data before being suspended from Twitter in 2022. Researchers have used it to measure the carbon footprint of private aviation. Governments have used it to identify aircraft violating airspace restrictions.

All of this flows from a single design decision embedded in the ADS-B standard: aircraft position data is a public broadcast, not a controlled transmission. The architects of ADS-B designed it for air traffic controllers in a world where the infrastructure required to receive it was expensive and specialized. A $35 Raspberry Pi and a $20 antenna can now do the same thing. That democratization was not anticipated.

HOW TO USE IT DIFFERENTLY

Most travelers use FlightRadar24 to answer one question: Is my flight on time? It answers considerably more. The playback function replays any completed flight’s track, making the cause of a delay visible: a slow climb-out indicates congestion at origin; a holding pattern indicates congestion on arrival; a southern oceanic deviation indicates jet stream avoidance.

The altitude and speed data visible in the app explain why the flight path looks the way it does. Transatlantic flights do not fly directly between the origin and the destination. They fly the North Atlantic Tracks — a set of routes published daily by Shanwick Oceanic Control and Gander Oceanic Control, optimized for the jet stream’s position. A westbound transatlantic flight in winter often curves far to the south to avoid the jet stream headwind. An eastbound flight curves north to use it as a tailwind. FlightRadar24 makes this routing visible in real time.