The data that FlightAware first receives for most commercial flights is sometimes delivered a year in advance via schedules published by the airlines. That data then usually remains unchanged until a few hours before the flight. Pilots or air traffic control operators controlling airspace on the route of flight will push out new data with a flight plan that provides specific details about the planned routing, altitude, and speed of the plane. But that’s where the static data end and the real-time data begin.
“When the door is shut and the parking brake is released by the pilots, the aircraft or airline will send us an ‘out’ message that indicates it’s pushed back from the gate, and we know that departure is imminent,” says FlightAware’s Baker. “As soon as the weight is lifted off the landing gear, we often get an ‘off’ message from the airlines or the aircraft itself that indicates the plane is airborne or a departure notice from air traffic control.”
Once en route, FlightAware continues to get position updates from the plane via radar installations at air traffic control centers and via ADS-B, along with continued updates on the plane’s route from air traffic control. All of this information is then fused together by FlightAware’s software, which uses it to determine the plane’s estimated time of arrival, and then displays the aggregate data for the flight on its website and in its apps.
“We detect the landing either by seeing the plane slow down below flying speed, by getting an ‘on’ message from the airplane, or by receiving an arrival notice from air traffic control. From there, we may have surface coverage to track the taxiing on the ground, and eventually receive the ‘in’ message from the airline indicating it’s safely parked at the gate,” says Baker.
Now multiply all the above steps by the thousands, or one for each plane in the sky across the world at any given time, and you’ll begin to appreciate the amount of data that fight tracking websites’ servers and algorithms are crunching each and every second.
https://www.fastcompany.com/3044490/how-flight-tracking-apps-work