(CNN) – On an average day, more than 200,000 flights take off and land around the world. That includes commercial, cargo and charter planes — which make up about half of the total — as well as business jets, private jets, helicopters, air ambulances, government and military aircraft, drones, hot air balloons and jetliners.
Most of them are equipped with a transponder, a device that communicates the plane’s position and other flight data to air traffic control, and that signal can be picked up with inexpensive receivers based on a technology called ADS-B. , for Transmission of Automatic Dependent Supervision. That’s what flight tracking websites do in a nutshell, providing users with a real-time snapshot of everything in the sky (minus a few exceptions).
An ADS-B receiver manufactured by Flightradar24.
The plane, a military version of the Boeing 737 called the C-40, took off from Kuala Lumpur in Malaysia before taking a circuitous route to Taiwan to avoid encounters with the Chinese military, adding hours to the flight. It did not immediately make it clear what the final destination would be, sparking chatter online as the plane slowly turned north towards the island. As a result, it was the most watched flight of all time on Flightradar24, with 2.92 million people watching at least part of the seven-hour journey.
The website, part of a group of popular flight-tracking services along with FlightAware and Plane Finder, was founded in Sweden in 2006 “quite by accident,” says FlightRadar24 communications director Ian Petchenik, as a way to run traffic to a flight. price comparison service.
Before Pelosi’s flight, the record for the most tracked flight on Flightradar24 belonged to Russian opposition leader Alexei Navalny’s return trip to Russia, where he was to be imprisoned. The January 2021 flight was tracked by 550,000 people, beating a previous record set in April 2020, when almost 200,000 users watched a Boeing 777 draw the crescent and star symbols of the Turkish national flag in the sky over Ankara to celebrate 100 anniversary of Turkey. sovereignty.
Previously, in September 2017, thousands of people watched a brave Delta Boeing 737 fly straight into Hurricane Irma to land in Puerto Rico and take off 40 minutes later for JFK, carefully positioning itself in the gaps between the wings of the hurricane.
However, outside of big events, the number of people following flights is constantly growing: “We see a lot of people using the site to track a loved one, track their flight or find the inbound flight they’re going to . to be later that day, to make sure the plane will come,” says Petchenik.
“Another use case is people who are very interested in aviation, or really like to follow certain types of aircraft. They can also go to the airport, pull up the app and see what’s coming. Then you have people who are professionally invested in the aviation industry because they own an aircraft and lease it, or because they have a fleet of aircraft and want to control them.Finally, there are people who are professionally invested in having a lot of flight data. This is airlines, airports, aircraft manufacturers using big data sets to gain industry insights.”
How data is collected
To collect the data, Flightradar has built its own network of ADS-B receivers, which it now says is the largest in the world with around 34,000 units, covering areas as far away as Antarctica.
Flightradar24 has receivers all over the globe, including places as far away as Antarctica.
About a quarter of the receivers are built by Flightradar24 itself, but most are collected by enthusiasts who provide the data on a voluntary basis. Because building a receiver is relatively cheap — components cost a total of about $100 — many have registered since Flightradar24 began opening its network to the public in 2009.
A dense array of receivers is essential to track flights globally, but there is an obvious problem with the oceans, where the network becomes sparse. So how do you get coverage on open water?
“Finding islands wherever we can and making sure we have takers there,” says Petchenik. “But recently we’ve moved back to satellite-based ADS-B receivers to be able to better track aircraft over the ocean. However, the most dominant data source is still our ground network.”
Having such a granular and localized amount of data can be useful to get an early insight into emergencies and accidents: “We store everything that comes in on our servers and if necessary we can go back to a specific receiver and extract the raw data. This is usually only done if an accident has occurred or if we have a request from an air navigation service provider or an accident investigation branch,” says Petchenik.
Not all data is available for every aircraft, however, as it depends on the type of transponders and receivers involved.
Aircraft owners or operators may also decide to prevent their data from being publicly displayed, most commonly for military, government or private aircraft. For example, they can sign up for a program like LADD, for Limiting Aircraft Data Display, which is maintained by the Federal Aviation Administration: “We stick to that list,” says Petchenik.
“This allows operators to have their data displayed differently, anonymously or, in some cases, not displayed at all. Of the total number of aircraft we track on a daily basis, about 3% have some sort of display adjustment of data.”
Top image: A Boeing C-40C carrying US House Speaker Nancy Pelosi takes off from Taipei Songshan on August 3, 2022, one day after Flight SPAR19 became Flightradar24’s most tracked flight ever.