Airport operations run according to take-off and landing slots. The boom in air travel following the pandemic shows no signs of slowing down anytime soon – in fact, according to the International Air Transport Association (IATA), demand for air travel is expected to grow 3.8% year-on-year for the foreseeable future, with an estimated four billion more passengers in 2043 than today.
Photo: Wenjie Zheng | Shutterstock
A number of key European airports, in particular, are predicted to be operating at full capacity in the not-so-distant future, and in order to support smooth operations at some of the world’s busiest and most congested airports, slots are needed. Let’s take a closer look at airport slots and examine how they are allocated to airlines.

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What is an airport slot?
IATA defines an airport slot as “a permission given by a coordinator for a planned operation to use the full range of airport infrastructure necessary to arrive or depart at a Level 3 airport on a specific date and time.” For slot purposes, airports are categorized into three different levels, depending on the scale of their operation and their need for slots. The different levels can be defined as below:
- Level 1 – slots are not needed to accommodate the flight schedule.
- Level 2 – slots are not required, but there is potential for congestion, so the airport makes voluntary use of them at peak times of the day/year in order to assist with planning and to ensure a smooth operation.
- Level 3 – highly congested airports where slots are a necessary planning tool, and where all airlines must have an allocated slot for departure and arrival.
Photo: Delta Air Lines
Airport slots were first developed in the 1960s, when commercial air travel started to become more and more popular, and are different from air traffic control (ATC) slots. Worldwide, almost 200 airports are categorized as Level 3 for slot purposes, accounting for up to 50% of global air traffic. According to data from IATA, around 35% of all flights operate between two Level 3 airports.
Such airports include the likes of New York John F. Kennedy International Airport (JFK), New York LaGuardia Airport (LGA), London Heathrow Airport (LHR), Amsterdam Schiphol Airport (AMS), Paris Charles de Gaulle Airport (CDG), Melbourne Airport (MEL), Beijing Capital International Airport (PEK), and Bogotá El Dorado International Airport (BOG).
Photo: NYC Russ | Shutterstock
At such airports, larger aircraft such as the Airbus A380 and Boeing 777 have come into their own, allowing airlines to transport a large number of passengers using as few slots as possible. That said, the world’s largest operator of both aircraft is Emirates, based at Dubai International Airport (DXB). Despite being the busiest airport in the Middle East, Dubai International Airport is classed as a Level 2 airport, meaning that slots are either not needed, or only needed at certain times of the day/year.

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How are airport slots allocated?
When it comes to slot allocation, there are three key players – the airport, airlines, and the slot coordinator. IATA summarizes the slot process on its website, saying,
“The slot process is designed to optimize the flying schedule through synchronized activities referred to as slot coordination. The coordination process is highly reliant on the system of coordinated airports all working to the same rules and timelines globally, ahead of each season. This ensures all airlines can secure the slots needed on each end of the route to operate a viable flight, considering flight times and aircraft fleet changes. The process is immune from discrimination, serving all types of airport and airline business models equally.”
Airport slots are managed by independent coordinators in order to provide a fair and non-discriminatory distribution. The Worldwide Airport Slot Guidelines (WASG) provide guidance on slot management and coordination, and are managed by the Worldwide Airport Slots Board (WASB). The WSAG has seven key aims, as published on IATA’s website:
- “To facilitate consumer choice of air services, improve global connectivity and enhance competition at congested airports for passengers and cargo.
- “To provide consumers with convenient schedules that meet demand, are consistent from one season to the next, and reliable in terms of their operability.
- “To ensure that slots are allocated at congested airports in an open, fair, transparent and non-discriminatory manner by a slot coordinator acting independently.
- “To realize the full capacity potential of the airport infrastructure and to promote regular reviews of such capacity and demand that enable effectual capacity declarations for slot allocation on a seasonal basis.
- “To balance airport access opportunities for existing and new airlines.
- “To provide flexibility for the industry to respond to regulatory and changing market conditions, as well as changing consumer demand.
- “To minimize congestion and delays.”
The appointed slot coordinator for Level 3 airports must be fully independent of any interested party and must act in a neutral manner. In the US, the Federal Aviation Administration (FAA) fulfills the role of slot coordinator.
The slot coordinator will monitor airlines and their adherence to their allocated slots, in line with strict usage rules. Meanwhile, IATA states that the role of the airport is “to identify and declare the maximum available slot capacity, including new capacity and existing capacity, considering the facilities and their capabilities. The airport is then responsible for delivering the declared capacity in the operational phase. This is a critical role because under-declaring or under-delivering capacity reduces the airlines’ ability to meet consumer demand.”

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The IATA Slot Conference
Each year, IATA holds two slot conferences in different locations every year (in June and November/December), with a view to discussing and assigning slots at Level 3 airports for the seasons ahead – at June’s slot conference, slots are allocated for the upcoming winter season, while those for the following summer season are allocated at December’s slot conference.
Photo: HarrisonKim1 | Shutterstock
Each IATA Slot Conference attracts more than 1,300 delegates from around the world, representing over 200 airlines. According to IATA, the goal of each conference is “for airlines to obtain the slots that will give them the best possible schedule to offer their customers at coordinated airports.” The conferences began in 1948, and are today among IATA’s largest events. The locations of recent and upcoming IATA Slot Conferences are shown below:
- June 2022 – Seattle
- November 2022 – Melbourne
- June 2023 – Dublin
- November 2023 – Dubai
- June 2024 – Bogotá
- November 2024 – Singapore
- June 2025 – Vancouver
- November 2025 – Lisbon
- June 2026 – location TBC (Asia & Oceania)
- November 2026 – location TBC (Africa & Middle East).

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The slot allocation process
According to the FAA, there are a number of steps involved in the slot allocation process for Level 3 airports in the US, which are outlined below:
- The slot coordinator (the FAA in this case) must provide airlines with the details of the status of historic slots by a given deadline.
- Airlines then have a window in which they can contest any of the FAA’s historic slots.
- The next deadline for carriers to consider is for them to submit any requests for priority consideration or to claim any additional historic slots.
- Airlines and other interested parties are able to book their attendance at one of IATA’s two annual slot conferences.
- The FAA then releases draft slot allocations for the upcoming season.
- Airlines are then able to meet with the FAA and other slot coordinators from around the world to discuss their slot allocation and schedule plans.
- IATA holds one of its two annual slot conferences, the location of which varies each time.
- Carriers must then return any slots they do not intend to operate for the upcoming season.
- The Historic Baseline Date marks the date at which any new slot allocations become effective.
Photo: Alaska Airlines
The slots at each airport can be allocated individually or in a series (five or more slots), and airlines have the right to maintain a series of slots from the previous year, on the condition that it operated at least 80% of them (known as historic precedence). Slots can be swapped and transferred between airlines, or used as part of a shared operation (for example, codesharing), and in order to avoid confusion when looking at routes that fly across multiple regions and time zones, airport slots are always allocated in UTC.

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