As well as aviation enthusiasts, anxious parents awaiting the return of their offspring from international trips, and Travel Tomorrow reporters verifying aviation sector news, more and more ordinary people are turning to flight tracker websites to follow the progress of aircraft in the skies. Tracking spikes when the world faces a security crisis such as the recent US and Israel attacks on Iran, and Iran’s retaliation on targets in the Persian Gulf. But how do these tracking websites work?
With increasing numbers of people undertaking international travel, it’s perhaps no wonder that more of us have a vested interest in the safe progress of flights. But behind that possibility is a shift in technology that has made airborne planes visible to the masses—the evolution from radar to transponders (a portmanteau word marrying transmitter and responder), to satellites.
Transponders essentially do exactly what the name suggests: they respond to a signal received, by transmitting another signal. Where radar is passive, simply bouncing a radio wave off a surface, a transponder actively receives a signal and responds in code; in the case of aviation, sending identification and altitude information.
Flight tracking websites rely on these unencrypted signals via 1090 MHz, as well as satellites. The Automatic Dependent Surveillance–Broadcast (ADS-B) is, the US Federal Aviation Administration (FAA) explains, “a modern satellite-based aviation surveillance technology where aircraft determine their own position (using GPS) and automatically broadcast it, along with ID, altitude, and velocity, to ground stations and other aircraft”—and satellites, which make the data widely available.
ADS-B: Automatic Dependent Surveillance-Broadcast
— Ray Aero (@ray__aero) February 27, 2026
An aviation technology used for aircraft tracking using transponders on the aircraft and recievers mostly on the ground while some a now in satellites for better coverage.
The system runs automatically without extra manual input…
Simple Flying points out that the US and Europe now demand that all commercial aircraft install ADS-B technology, feeding into “Next Generation” air traffic control upgrades and the Single European Sky ATM Research (SESAR) project. The joint effort by the EU, EUROCONTROL, public and private, civil and military aviation stakeholders is intended to manage air traffic “interoperably” and optimise it “so that airspace users can fly safely the most efficient trajectories and that new flying vehicles (such as drones) are safely integrated in all classes of airspace,” a European Commission Directorate-General for Mobility and Transport explains.
Right now though Flightradar24 estimates that 70% of all commercial traffic is fitted with an ADS-B transponder. Those signals are picked up by aviation enthusiast volunteers who host and operate ADS-B receivers and ensure the data is fed to the tracking websites that are seeing such growth in popularity. Receivers must be distributed at least every 250-450 km in all directions, Simple Flying notes, but Flightradar24 claims to have grown 100% coverage in the two decades since its launch. So-called “multileration,” or MLAT also contributes to the tracking system, calculating the position of aircraft by working out time differences between signals received.
This means, as Euronews has reported, that 140,000 people were able to track “a single flight from Dubai International Airport to Mumbai” in real time when hostilities broke out between the US, Israel, and Iran. Football fans too, or perhaps football haters, tracked Cristiano Ronaldo’s flight from Saudi Arabia to Spain, checking his progress. Whether the surge in interest is effectively a new form of “car crash television” or reflects a real interest in aviation, is information yet to be triangulated.
