Airport Slots: How Airlines Secure Landing Rights at Congested Airports

At many of the world's busiest airports, you cannot simply decide to fly there — you need a slot. An airport slot is a permission to use an airport's infrastructure (runway, terminal, gates) at a specific time. At the most congested airports, slots are among the most valuable assets in the airline industry.

How slots work

Slots are allocated twice annually (for the northern hemisphere summer and winter schedules) through a process coordinated by IATA at airports designated as Level 3 (fully coordinated). Airlines must apply for the slots they want, and coordinators try to match requests with available capacity. Historical usage gives incumbent airlines priority — carriers that hold a slot from the previous equivalent season have grandfather rights to keep it if they use it at least 80% of the time.

The world's most slot-constrained airports

• London Heathrow (LHR) — operating at essentially 100% capacity, with no meaningful slack in the system
• Paris Charles de Gaulle (CDG)
• Frankfurt (FRA)
• Tokyo Narita (NRT)
• New York Kennedy (JFK)

The value of slots

Because slots at constrained airports cannot be created (physical capacity is fixed), they trade at extraordinary prices. A pair of peak-hour slots at Heathrow — one for landing, one for takeoff — has sold for over $75 million in secondary market transactions. This scarcity drives much of the strategic behavior in the airline industry, including why airlines sometimes operate near-empty "slot-keeping" flights rather than risk losing valuable slot pairs.