The
Morning Bank

Twice a year, somewhere in the world, about 1,300 people check into a conference centre to divide up the sky.

The IATA Slot Conference has been running since 1948. The 158th was held in Bangkok in June 2026; the 159th, shaping schedules for 2027, is scheduled for Budapest on 17–19 November 2026. Representatives of more than 250 airlines and the coordinators of over 300 capacity-constrained airports sit at tables and negotiate, face to face, over who lands where and when. It is one of the largest events the airline industry stages, and it is, in effect, a long-running marketplace in aviation, for a commodity that the law is adamant is not a commodity.

What is being negotiated is a slot: a permission. Under the regulation that governs allocation in Britain - Council Regulation (EEC) No 95/93, inherited into UK law after Brexit and amended several times since - a slot is "the permission given by a coordinator... to use the full range of airport infrastructure necessary to operate an air service at a coordinated airport on a specific date and time for the purpose of landing or take-off". The Department for Transport glosses it identically in its own 2024 consultation: permission to use the runway, the terminal, the gates, at a named moment.

Permission. Not a lease, not a title, not a right in land. The word is doing deliberate work, because the holder has conditional access to infrastructure, not ownership of it. American regulators are blunter: the Federal Aviation Administration describes a slot as an operating privilege subject to its control rather than a property right.

In Britain the permissions are issued by Airport Coordination Limited, a company registered in Staines in April 1991, limited by guarantee and with no share capital, which describes itself as a not-for-profit body founded on independence and non-discrimination. It coordinates around eighty airports worldwide. At Heathrow, Gatwick, Stansted, Luton and City - all Level 3, meaning demand so exceeds capacity that no aircraft may move without an allocated slot - ACL is the gate.

And the rules it applies look, on paper, like a competitive system. Unused slots go into a pool. Half of everything in that pool must be offered first to new entrants, so that incumbents cannot pull up the ladder behind them. The baseline for historic rights is the 80:20 rule, known in the trade as use it or lose it: fly a series of slots at least 80% of the time across a season and you keep it next season, fall below without qualifying relief and the series returns to the pool. Exceptions matter: Parliament considered temporary provisions in June 2026 allowing airlines to hand back up to 10% of slots for the summer and winter 2026 seasons without losing historic rights, in response to disruption from the Middle East conflict.

None of this was designed to create an asset. Grandfather rights - the principle that if you flew it last year you may fly it this year - began as scheduling housekeeping among a handful of flag carriers in an era when there was no shortage worth arguing about. It was a convention for avoiding collisions in a timetable, not a settlement of property.

But conventions calcify, and the shortage arrived.

To see what that capacity is worth, you need the moment the market discovered its own price, and that moment has a date: 30 March 2008.

Until then, access to Heathrow from the United States was not a market at all. It was a treaty. Bermuda II, signed on 23 July 1977, initially restricted the designated British and American Heathrow-US operators to British Airways, Pan Am and TWA. United and American later replaced Pan Am and TWA, and Virgin Atlantic gained access in 1991. Some other countries' carriers also held onward traffic rights. Access remained tightly restricted by agreement between two governments until 2008.

Bermuda II expired on 30 March 2008, replaced by the EU-US Open Skies agreement. Suddenly any qualifying carrier could fly Heathrow to America, provided it could get in. Continental Airlines got in by buying four daily slot pairs for a reported $209 million, a figure recorded in the European Commission's impact assessment. Roughly $52 million per daily pair, in 2008 money, for permission that had been handed to the incumbents for nothing.

That is one of the clearest documented benchmarks in this market, and it is not the number everybody quotes.

The number everybody quotes is $75 million, attached to a 05:30 arrival Oman Air acquired in February 2016. Follow it through the record and it comes apart in three stages. On 16 February 2016, ch-aviation reported that Air France-KLM had sold two Heathrow pairings, one of them to Oman Air at $75 million. Nine days later, Business Traveller reported that the seller had not been Air France-KLM at all: "News has emerged that it was Kenya Airways who sold Oman Air its prized early morning slot at London Heathrow. Initially it was reported that Oman Air acquired the slot from the Air France/KLM Group." Then Aviation Week reported the shape of the transaction: Oman Air was taking two Boeing 787-8 Dreamliners from Kenya Airways on a three-year wet lease alongside the slot, as Kenya Airways scrambled for cash.

So the most cited figure in British aviation was reported against the wrong counterparty, circulated without a published contract or price breakdown, alongside reports of a wider agreement involving two widebody aircraft. That does not establish that the aircraft leases were included in the $75 million; it does make the figure harder to interpret as a clean comparison.

That confusion is what an opaque market makes possible. ACL records who holds a slot and who operates it, and does not record, regulate or publish what was paid. There is no comprehensive public price register or requirement to advertise availability and cost. The DfT's own verdict is unusually undiplomatic: with no requirement to advertise either availability or cost, the secondary market "lacks the basic features of a transparent modern marketplace". The department also notes why capacity sits unused in plain sight - airlines "prefer to hold on to even 'loss-making' slots rather than selling them, in order to hinder competitors from obtaining slots".

The volumes are tiny. In summer 2019, 2.4% of Heathrow slots traded. At Gatwick, 0.8%. This is not a liquid market; it is a rare and private one, which is why a single disputed transaction from 2016 has been doing the work of a price index for a decade.

Where the value stops being deniable is on balance sheets, and there it appears only in half. Under international accounting standards an airline that buys a slot capitalises it at what it paid, and slots judged to have indefinite useful lives are not amortised, but are tested annually for impairment. An airline handed a slot for nothing has no cost to capitalise, so the original allocation does not generate a purchase price to record. Purchased slots therefore show up at tens or hundreds of millions. Inherited slots show up at zero. British Airways holds roughly half the slots at Heathrow, but the carrying value of purchased slots does not measure the market value of its entire holding.

Lenders are not fooled by the accounting. In November 2025, Apollo-managed funds and affiliates completed a $745 million senior secured financing backed by Virgin Atlantic's Heathrow slot portfolio. Etihad paid Jet Airways $70 million for three Heathrow pairs in 2013 and leased them straight back, using a sale-and-leaseback arrangement to release cash while retaining access. Banks have no difficulty valuing permissions that are not ownership of the runway.

And the bill lands somewhere specific.

In June 2022, Frontier Economics reported to Heathrow Airport on slot scarcity and ticket prices. Its modelling estimated a congestion premium on Heathrow fares: around 20% before the pandemic, worth over £30 a head on a short-haul return and over £200 a head on a long-haul return. Across point-to-point passengers, roughly £2 billion a year before the pandemic. These are modelled averages, not a fixed surcharge on each ticket. Heathrow commissioned the work and had an interest in showing that airlines capture scarcity rents; the estimate should be read with that incentive in view.

The estimated rent generated by constrained runway access runs into billions. It accrues through airline fares, rather than through payments to the airport for slot transfers. Heathrow receives nothing when a slot changes hands: not a fee, not a percentage, not a levy. Its airport charges are capped by the Civil Aviation Authority under a regulated asset base model. The concrete is regulated. The permission to use the concrete is not.

One qualification, because the strong version of this claim is wrong. The state is not entirely absent. Ordinary taxes can apply to airline profits and slot transactions. What is absent is a dedicated public charge capturing the scarcity value when the permission changes hands.

Therefore the question of who holds these permissions stops being administrative, because for some countries the slot is the connection.

Kenya Airways sold its valuable early-morning Heathrow slot. That is the detail the $75 million story usually loses. A national flag carrier's prime arrival time at a major long-haul destination was converted into liquidity during a cash crisis, and by 2024 the Kenyan press was reporting that the sale had damaged the airline's competitiveness on the route. It could not count on recovering an equivalent morning slot from a nearly empty pool.

In August 2024, Romania's state-owned TAROM sold its Heathrow slots to Qatar Airways. The daily Bucharest-Heathrow service, flown by an Airbus A318, ended with the switch to the winter timetable on 27 October 2024. Qatar put a Boeing 777-300ER into the same times on its Doha route. Romania's national carrier had been in restructuring, with state aid approved by the European Commission on conditions that included cutting routes. The country's flag-carrier link to London became a Doha flight, and the proceeds went into an airline's restructuring.

By October 2024 South African Airways was reported to be weighing the same move on slots it had been leasing to Qatar Airways and British Airways, to raise capital. An SAA representative offered the reasoning that every distressed carrier eventually reaches: "Even during our peak operations to London, we were only utilising one of these landing slots."

Each of those decisions is defensible on its own terms. Together they describe something odd: a country's scheduled access to the British capital is an asset on a private balance sheet, it is worth more to a solvent foreign carrier than to the airline holding it, and it moves in the direction of capital. The treaty restrictions have been replaced by an auction with no auctioneer, in which historic allocations were entrenched by the 1993 regulation and the bidding is private.

This is also why expansion is a more complicated proposition than it looks. A third runway would lift the cap from 480,000 movements to around 756,000, and capacity from roughly 84 million passengers to 150 million. In November 2025 the government backed Heathrow's own scheme over a rival from the Arora Group, at about £33 billion for the runway and £49 billion for the wider project, with a development consent decision targeted before the end of this parliament and the runway perhaps operating in 2035. The government launched consultation on a draft Heathrow Expansion National Policy Statement in June 2026. The CAA has since confirmed recovery of early expansion costs up to £320 million in 2024 prices, subject to safeguards.

Adding a quarter of a million movements a year to a market where sixteen slots reached the pool in a season does not merely reduce scarcity. It could erode the premium that scarcity sustains, putting pressure on balance sheet values, collateral, and the barrier that keeps challengers out - while the incumbents also pay the regulated charges that fund the concrete. Their enthusiasm for more Heathrow has been notably cooler than one might expect from businesses being offered room to grow.

The reform proposals have the same shape. The DfT's consultation canvassed tightening the usage rule from 80:20 to 90:10, building a slot register with a mandated trading platform, and restricting what can be done with newly allocated slots. It is a serious document that names the problem accurately. Its treatment of new capacity does not amount to auctioning away the existing historic allocations. In June 2026, Parliament was also debating slot-reform powers in the Civil Aviation Bill, with ministers defending the predictability of historic rights. Reform remains politically live; proposals and enabling powers are not a completed redistribution.

Auctioning has been the economists' answer since the DotEcon study for the European Commission in 2001, and has never been implemented in Europe. The objections are substantive rather than merely self-interested: fleets and networks have been planned for decades on the assumption of historic precedence, confiscation would land on balance sheets banks have lent against, and a bidding war for London could be won by the deepest state-backed pocket rather than the best operator. The Commission's 2011 attempt at reform died in the Council. The rule survives because everyone with standing to object has a reason to, and passengers paying the estimated premium have no slots to bargain with.