Grandfather rights and use-it-or-lose-it
At congested airports, take-off and landing slots are allocated by an independent coordinator. The governing principle is historic precedence: an airline that used a slot series for a season retains the right to it the following year, provided it used it at least 80% of the time. That is the famous 80/20 rule, and failing it means the slot returns to the pool.
The rule is why airlines have historically flown near-empty "ghost flights" to protect slots — and why the rule was suspended and then phased back in during the pandemic, when flying empty aircraft to retain rights became indefensible.
The value
Heathrow is the clearest case, operating at effectively full capacity with no room for additional movements. Slot pairs there have reportedly changed hands for tens of millions of pounds — a peak-time pair was reported at around $75m in 2016, one of the highest prices ever paid for a pure right.
The value reflects scarcity and the profitability of the routes a peak slot enables. Early morning arrivals from long-haul destinations are the most valuable, because they connect into the day's departure bank.
Not ownership
Slots are not property in law. They are administrative permissions. Yet they appear on airline balance sheets as intangible assets, are used as collateral, and were among the most valuable assets in several airline insolvencies. When Monarch collapsed in 2017, the question of whether its administrators could sell its slots went to the Court of Appeal — which found they could, worth a reported £60m, materially improving creditor recovery.
This gap between legal characterisation and commercial reality is the defining feature of the asset.
Secondary trading
EU and UK rules historically permitted slot exchanges but were ambiguous about outright sales for cash. A 1999 English court decision effectively legitimised monetary transfers structured as exchanges, and a functioning secondary market developed on that basis. Reform of the slot allocation framework has been consulted on repeatedly without fundamental change.
How you would actually trade it
Airlines only. Transfers are negotiated bilaterally and must be notified to and recorded by the coordinator, which at UK airports is Airport Coordination Limited.
Competition authorities intervene where slot transfers affect market concentration, and slot divestment is a standard remedy imposed on airline mergers — which periodically forces valuable slots onto the market at regulated terms.
What goes wrong
- Regulatory reform could replace grandfathering with auctions, eliminating the value of incumbency.
- Use-it-or-lose-it requires actually operating the flights.
- Not legally property, which creates uncertainty in insolvency and security arrangements.
- Capacity change. A new runway would dilute scarcity value substantially.
- Environmental policy on aviation growth is a live long-term threat.
This entry describes how a market works. It is not a recommendation, a price forecast, or advice about whether this belongs anywhere near your money. How entries are written.