Live aircraft-tracking radar aggregates data from various sources, including the Federal Aviation Administration and automatic dependent surveillance-broadcast technology, which allows pilots to keep up with air traffic from around the world in real time. Pilots also use live aircraft-tracking radar to communicate with air traffic controllers on the ground.
Automatic dependent surveillance-broadcast is the primary technology used in live aircraft-tracking radar services, such as Flightradar24. This technology uses a GPS navigation source to determine the location of a flight. The data is then sent as a signal by the ADS-B transponder on the aircraft. The ADS-B receiver then picks up the signal and transmits it to the radar-tracking service provider. ADS-B tracking radar systems are in place on about 70 percent of commercial aircraft and 20 percent of general aviation craft as of 2015. However, the technology is not consistently used by air traffic control, and receivers are not in place at all locations across the globe.
Because radar facilities, which are located on land, have a tracking radius of only about 200 miles, pilots also use satellite-based voice communication and text-data networks to report to their positions to air traffic controllers when they are over water and out of range.