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Explainer: How do aircraft tracking sites do their job?

Even before official confirmation of the crash of a China Eastern flight, aviation geeks and experts were on flight tracking websites for a glimpse of the flight’s fatal descent. Moneycontrol explains how these websites work.

March 27, 2022 / 12:45 PM IST
China Eastern Airlines plane crash: Flight Mu5735 did not have any survivors. (Image: ChinaAvReview/Twitter)

China Eastern Airlines plane crash: Flight Mu5735 did not have any survivors. (Image: ChinaAvReview/Twitter)

On March 21, a China Eastern Airlines domestic flight, on its way from Kunming to Guangzhou, descended sharply in mid-flight and crashed, killing all 123 passengers and nine crew.

Without any survivors, the focus was on retrieving the so-called black box – an orange-coloured box that contains flight data and the cockpit voice recorder.

Even before the crash was officially confirmed and CCTV videos started doing the rounds, aviation geeks and experts took to flight tracking websites like FlightRadar24 to see the plane’s sharp dive from 29,000 feet.

There have been times when an aviation incident or accident has taken place and FlightRadar24 or similar websites like FlightAware or RadarBox have had to say they were not tracking the particular flight at the time it occurred.

Most of these sites, including Flightradar24, Radarbox and FlightAware, started as small-time flight tracking websites and have been trying to climb up the ladder.


From making it a paid service for users to offering additional features to having airlines and airports as their clients, they have grown steadily. This has also meant collaboration with authorities in various countries, sometimes on a quid pro quo basis.

FlightAware receives data from air traffic control systems in over 45 countries, FlightAware's network of ADS-B ground stations is present in 195 countries. ADS-B is short for Automatic Dependent Surveillance-Broadcast.

ADS-B, manufactured by the American company Aerion, has a datalink (satellite/VHF) with every major satellite communication provider, including ARINC, SITA, Satcom Direct, Garmin, and Honeywell GoDirect. Here is a look at how flight tracking works.

ADS-B: The primary source of data

Primarily, these websites use ADS-B. An aircraft get its location from a GPS navigation source (like a satellite). Planes that have ADS-B transponders transmit signals containing the location, altitude, type of aircraft and just about anything it transmits. This data is crowd-sourced with the help of a receiver connected to respective sites, which feed the data to a server and then it appears on the website and mobile applications.

The technology is still evolving and Air Traffic Control systems still rely on a mix of primary and secondary radars for managing traffic. The coverage of these receivers is restricted to anywhere between 200 km and 450 km, depending on the terrain and the height at which the receiver is placed. This also makes tracking difficult over vast oceans and polar routes.

The older generation aircraft are without ADS-B transponders and one would notice that the ATR 72-500 series does not show on all flight tracking sites but the ATR72-600 does show up, thanks to the ADS-B transponder in the latter. Many general aviation aircraft are without this transponder, making it difficult to notice them on flight tracking websites.

ADS-B has been standard equipment for aircraft manufactured from 2020.

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Ameya Joshi runs the aviation analysis website Network Thoughts.
first published: Mar 27, 2022 12:44 pm
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