Slot

Slot is a permission to use a runway for takeoff or landing at a specific date and time at a slot-controlled (coordinated) airport. Slots are necessary at airports where demand exceeds capacity.

Slots are allocated by airport coordinators following IATA Worldwide Slot Guidelines. Airlines can hold, exchange, or (in some markets) trade slots. Historically allocated slots (grandfather rights) are retained as long as the airline uses them at least 80% of the time (use-it-or-lose-it rule). Slots at premium airports (Heathrow, JFK, Haneda) are extremely valuable assets.