During major crises or airspace closures, interest in flight tracking sites spikes. Platforms like Flightradar24 and FlightAware allow users to track aircraft movements around the world in real time.
Although it works like magic, behind it is a combination of several technologies for collecting and processing flight data.
ADS-B transponders and receiver network
The basic technology that enables aircraft tracking is called Automatic Dependent Surveillance‑Broadcast or ADS-B for short. Most modern passenger aircraft are equipped with an ADS-B transponder that continuously transmits flight information. This data includes the aircraft’s position, flight altitude, speed and aircraft identification number.
The signal emitted by the aircraft is picked up by ground-based ADS-B receivers distributed around the world. These receivers then forward the data to the servers of platforms such as Flightradar24. Today, this company has a network of about 50,000 receivers all over the planet.
In addition to ground stations, satellites are also used that can receive the ADS-B signal, which is especially important for flights over the ocean where there is no ground infrastructure.
MLAT technology for older aircraft
Some older aircraft do not use ADS-B, but an older type of transponder known as Mode S. In these cases, a method called Multilateration or MLAT is used.
This technique works by having at least four receivers on the ground pick up the same aircraft signal. The difference in signal reception time at each location is then measured. Based on these differences, the system calculates the exact position of the aircraft in space.
MLAT has limitations because it requires a large number of receivers and a sufficient flight height, which is why planes sometimes “disappear” from the radar during takeoff or landing.
In situations where no ADS-B or MLAT data is available, flight tracking sites use estimates based on the flight plan and last known position of the aircraft. Then the route shown may be approximate and not completely accurate.
During military conflicts, a technique known as GPS jamming is often used. In this case, the devices emit a strong signal on the same frequency as GPS and thus block the reception of the real signal.
There is also the so-called GPS spoofing, where a fake GPS location is sent to trick the system into wrong data. Because of this, unusual flight patterns such as zigzag lines or circular paths can sometimes be seen on maps. To reduce these problems, platforms like Flightradar24 combine multiple technologies, including ADS-B, MLAT and other data sources, MSN reports.