The OpenSky Network is a non-profit association based in Switzerland that provides open access of flight tracking control data.

[1] It was set up as a research project by several universities and government entities with the goal to improve the security, reliability and efficiency of the airspace.

Similar to many existing flight trackers such as Flightradar24 and FlightAware, the OpenSky Network consists of a multitude of receivers (currently around 2000,[2] mostly concentrated in Europe and the US), which are connected to the Internet by volunteers, industrial supporters, academic, and governmental organizations.

[3] All collected raw data is archived in a large historical database, containing over 23 trillion air traffic control messages (November 2020).

The main air traffic control communication technologies currently used by the OpenSky Network are the Automatic Dependent Surveillance-Broadcast (ADS-B), Mode S and, since late 2018, FLARM.