Airport slots and ATC slots: air traffic regulation

Airport slot and ATC slot: two different systems

The two are often confused, yet they follow opposite logics. The airport slot is an infrastructure reservation: it gives you the right to use the runway and facilities of a coordinated airport. The ATC slot, by contrast, belongs to traffic flow management: it tells you when you will actually be able to take off, based on airspace congestion.

In short: you can hold a valid airport slot and still receive an ATC slot that pushes back your departure. The first is prepared weeks in advance, the second appears on the day of the flight. The sections below cover each in turn.

The airport slot

The airport slot is governed by IATA's Worldwide Airport Slot Guidelines (WASG) and, in the European Union, by Regulation (EEC) No 95/93. It is allocated by an independent coordinator, per scheduling season (summer and winter). The request is made in advance, through the operator or the handling agent, to obtain the desired departure or arrival time. The time can then be changed, subject to acceptance of the new slot.

Not all airports work the same way. There are three coordination levels, summarised below.

Which European airports require slots?

Only Level 3 airports require an airport slot. The table below gives examples by country, with the relevant coordinator. This list is indicative and revised each season, with some airports coordinated only in summer.

Two useful clarifications. Lyon-Saint-Exupéry and Basel-Mulhouse are Level 2 airports: they do not require a mandatory airport slot. In London, Biggin Hill is not coordinated, which makes it an attractive option for business aviation, even though an ATC slot may still apply.

The ATC slot, or CTOT (EUROCONTROL regulation)

The ATC slot carries the technical name CTOT, for Calculated Take-Off Time. It is assigned by EUROCONTROL's Network Manager, whose operations centre in Brussels, the NMOC (formerly CFMU), balances demand and capacity across European airspace. A CTOT can appear as soon as the flight plan is filed, when the areas overflown or the airport are regulated.

A CTOT comes with a tolerance window of 5 minutes before to 10 minutes after the calculated time. It is not fixed: depending on how traffic evolves, it can improve, be revised or disappear. This is why our teams recommend being ready at the time originally planned: an ATC slot can ease, and missing it would cause further delay.

How these slots affect your private flight

In practice, the airport slot determines whether you can use a coordinated airport at the desired time, while the CTOT can shift the take-off on the day of the flight. During the busiest periods, summer towards the Mediterranean for example, the two constraints combine and planning ahead becomes decisive. Our feature on airport operational restrictions rounds out this overview.

The value of a broker and its operator is measured precisely here: requesting the right airport slot in advance, following the regulation in real time and adjusting the plan if needed. Using a business-aviation terminal, or FBO, also speeds up formalities, which helps to keep to a tight slot window.

IBC Aviation handles these constraints for you

As an independent broker, IBC Aviation compares the aircraft available on the market and coordinates every operational aspect of the flight, slots included. Our teams check slot availability before confirming a time and follow the regulation on the day of departure. You can discover our approach on our private jet charter page and browse our aircraft fleet.

Private jet charter with IBC Aviation:

Our teams advise you on the aircraft best suited to your itinerary and your needs, and handle airport slots and traffic regulation for you. Available 24/7:

• France: +33 1 41 69 88 88
• Switzerland: +41 22 880 28 88
• Dubai: +971 55 303 5161
• Bangkok: +66 81 808 2866
• Email: contact@ibc-aviation.com

Frequently asked questions

What is an airport slot?

It is the right to use the infrastructure of a coordinated airport, known as Level 3, at a given time. It is allocated in advance by an independent coordinator, under Regulation (EEC) No 95/93 and IATA's guidelines.

What is the difference between an airport slot and an ATC slot?

The airport slot is an infrastructure reservation, planned in advance by season. The ATC slot, or CTOT, is a calculated take-off time imposed on the day itself by EUROCONTROL's Network Manager when airspace is congested. They are two distinct systems.

What is a CTOT?

The CTOT (Calculated Take-Off Time) is the take-off time assigned by EUROCONTROL's operations centre, with a tolerance window of 5 minutes before to 10 minutes after.

What is EUROCONTROL's Network Manager?

It is the EUROCONTROL body, based in Brussels (formerly the CFMU), that manages air traffic flows across Europe and assigns CTOTs to balance demand and capacity.

Can a slot delay my private flight?

Yes. A CTOT can impose a delay. It appears after the flight plan is filed, can improve or disappear, and missing it causes further delay. It is therefore advisable to be ready at the original time.

Which European airports require slots?

Level 3 examples include Paris-CDG, Orly, Nice, Geneva, Zurich, London-Heathrow and Madrid, as well as many islands in summer. The list is revised each season.

Is Lyon-Saint-Exupéry a slot-coordinated airport?

Not in the strict sense: it is a Level 2 (facilitated) airport, without a mandatory airport slot. An ATC slot may still apply if traffic is regulated.