“Ghost flights” carry neither cargo nor passengers. Their purpose is to retain so-called “slots” . These slots are exclusive take-off and landing timeframes at airports, allocated to individual airlines. If a slot is not regurlarly used, it is forfeited and gets assigned to other airlines. In order to prevent competitiors from getting these valuable slots, airlines simply simply take off empty. This results in thousands of ghost flights and their associated emissions.

“Slotmachine” continuously queries departure schedules from European airports and compares it with radar data from flight trackers. This is possible because aircrafts constantly broadcast their position to avoid collisions. Though a constant comparison of these data sets, ghost flights can be filtered out and get displayed live by "Slotmachine" on a departure display like the ones found at airports.