"Ghost flights" are flights operated with very few or zero passengers, primarily to serve a logistical or regulatory purpose. In many parts of the world, particularly in Europe, the "80/20" slot rule requires airlines to use their takeoff and landing slots at least 80% of the time to keep them. If an airline stops flying a route due to low demand, they risk losing that valuable slot to a competitor. Consequently, they fly empty planes just to "squat" on the slot. Beyond regulations, ghost flights occur for repositioning—moving an aircraft to a different airport where it is needed for a scheduled departure—or for maintenance reasons where the craft must reach a specific hanger. During the pandemic, the environmental impact of these flights became a major point of controversy, leading to temporary suspensions of slot rules. Despite the criticism, ghost flights remain a byproduct of a rigid global aviation infrastructure where "use it or lose it" policies often clash with the industry's stated goals of reducing carbon emissions and operational waste.