Skyjacker is part of a relatively new genre of games called "mixed-reality gaming" where real life events, in our case live flights, cross over from real to fantasy and provide the input and realism for the game.
Skyjacker uses real-time data from flights operating around the world. Wherever a gamer is located in the world, they can point their phone at the sky and find and interact with airplanes flying nearby. These real flights are displayed in the game and can then be commandeered and even diverted, with players gaining points and notoriety dependent on the type of airplane they choose and which airport they decide to land the plane. Skyjacker is a location-based game making the entire world the game space with players from different countries and continents battling it out for the same airplanes as they fly to their destinations.
So where does flight data come from?
Amazingly much of this data is provided by thousands of enthusiasts worldwide who constantly upload their data to various flight data aggregators who then map out the world's air traffic. For less than £100, anyone can erect an antenna, install some software and 'see' aircraft flying in their vicinity. There are a number of different ways to do this, ranging from professional tracking receivers to building your own receivers.
In the next few years, worldwide data coverage will become more reliable as initiatives such as Global Space-Based ADS-B systems are launched and come online. Better tracking of airplanes is useful for airlines to monitor their fleets, airports to plan operations, give customers more up to date information, keeping enthusiasts happy and allowing gamers to skyjack more airplanes!