how to create a site

Basic Principles


With the onset of congestion during some periods of the day at a few major airports in the early 1960’s, the scope of the schedule discussions was broadened to cover the adjustments needed to reduce anticipated delays to an acceptable level. Where services planned during certain periods at an airport exceeded what the airport could accommodate without unacceptable delays, some services would have to be moved, usually with some economic penalty. This induced IATA (International Air Transport Association) to establish coordination offices at such airports, usually embedded within the organisation of the national airline. Over the years, a consensus developed as to which services should be moved, in fairness to all planning to operate during the period. The recommended procedures and priorities for such schedule adjustments are contained in the IATA Worldwide Slot Guidelines (WSG), first issued in 1976.

Airport Coordination

Airport coordination is a means of managing airport capacity through the application of a set of rules contained in the Worldwide Slot Guidelines (WSG). Coordination involves the allocation of constrained or limited airport capacity to airlines and other aircraft operators to ensure a viable airport and air transport operation. Coordination is also a process to maximize the efficient use of airport infrastructure.  The prime objective of airport coordination is to ensure the most efficient use of airport infrastructure in order to maximize benefits to the greatest number of airport users. For the purposes of airport coordination, airports are categorized by the responsible authorities according to the following levels of congestion:


Not Coordinated

Level 1

Airports where the capacity of the airport infrastructure is generally adequate to meet the demands of airport users at all times.


Schedules Facilitated

Level 2

Airports where there is potential for congestion during some periods of the day, week, or season which can be resolved by voluntary cooperation between airlines. A facilitator is appointed to facilitate the planned operations of airlines using or planning to use the airport.



Level 3

Airports where capacity providers have failed to develop sufficient infrastructure, or where governments have imposed conditions that make it impossible to meet demand. A coordinator is appointed to allocate slots to airlines and other aircraft operators using or planning to use the airport as a means of managing available capacity.

Coordination Principles

The coordination process between airlines and airport coordinators is described in the IATA Worldwide Slot Guidelines (WSG) which contains a set of procedures and time frames to provide guidance for the management of the allocation of scarce resources at busy airports. The communication between airlines and coordinators is outlined in the IATA Standard Schedules Information Manual (SSIM) which is constituted under IATA Passenger Services Conference Recommended Practice 1761b that was declared effective 1 July 1972. Standard message formats have been agreed to allow airlines, airport coordinators and schedule facilitators to exchange airport coordination and schedule movement information electronically. The message formats are integrated into an iterative (sequential) set of request and reply messages and have been designed to provide as much clarity as possible for the message users. The received message details can be processed either by computer or by manual methods. The rules for the use and composition of the messages, together with detailed specifications and examples, are explained in chapter 6 of the SSIM.

Airport Coordinator

A coordinator is appointed by the responsible authority, following consultations with the airport managing body, all airlines using the airport and their representative organizations. Coordinators must be functionally and financially independent of any single interested party and act in a neutral, transparent and non-discriminatory way.

Capacity Constraints

Performance and use of runway system, surrounding area (topography), approach and departure routes, air traffic control capabilities

Number of available ramp stands, restrictions on aircraft size, longterm parking

“passenger throughput”, check-in, arrival, transfer and baggage sorting/area infrastructure, security/customs & immigration facilities, Schengen and non-Schengen areas

Night ban, night curfews, noise restrictions, noise quotas

Security dispositions, special handling etc.

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque quis quam in risus pulvinar ultrices eget non sem. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae proin accumsan odio.

Definition of Slot

The airport slot is mandatory at coordinated airports for each movement (arrival AND departure) and is valid for a specific time at a specific weekday and for a specific period applied for. It is a permission given by the coordinator for a planned operation to use the full range of airport infrastructure necessary to arrive or depart at a coordinated airport on a specific date and time.
Allocated slot times are based on the planned on-block (arrival) and off-block (departure) times. Actual times of arrival and departure may vary due to operational factors.

Season Planning

Essential steps and principles for each season planning
  • Historical Precedence

    The core of the slot allocation process is the use of historical precedence ("grandfather rights"). This precedence applies only to equivalent, and not consecutive, schedules seasons (e.g. Summer to Summer season) and is limited to the equivalent period and days of operation. This principle entitles an airline to claim a series of slots within the same coordination parameter(s) in the next equivalent schedules season, provided that:
    a) the slots were allocated for regular scheduled services
    forming a series of slots,
    b) at least 80% of the slots were operated by an airline as
    cleared by the coordinator, and may include the observations and results of the seasonal slot performance monitoring
    (source: IATA Worldwide Slot Guidelines)

  • Submission for New Season

    About six month before the start of the respective schedules season, airlines provide coordinators with their schedule clearance requests for the arrival and departure times required at the airports concerned. The submission is sent by the airline to the coordinator as a defined standard message format, called SCR (Slot Clearance Request).

  • Initial Coordination

    The coordinator collates this information and identifies periods in which slot requests exceed declared airport capacities. Slots are allocated according to the recommendations of the IATA Worldwide Slot Guidelines and in Europe according to the respective EEC95/93 Council Regulation and amendments. All airlines are informed about their allocated slots latest 12 days prior to the start of the upcoming slot conference.

  • IATA Slot Conferences

    Organised by IATA, the Slot Conferences are held twice each year (June and November) about five months before the start of the respective schedules seasons. During the 3 days "working conference", schedules are adjusted mainly through bilateral meetings between airlines and coordinators regarding alternatives offered, or between airlines to exchange slots offered or accepted. A schedule change at one airport must affect one or more other airports. Because usually all coordinators attend the conference, it provides the best forum in which all such repercussive changes can be quickly and efficiently processed, and airlines can leave the conference with firm schedules which they consider are the best compromise between what is wanted and what is available. The entire process is based on consensus and aims to be flexible, fair and open.

  • Slot Return Deadline

    Airlines must not hold slots which they do not intend to operate, transfer or exchange, as this could prevent other airlines from obtaining slots. If an airline becomes aware that for whatever reason it may not be able to use a slot, or series of slots, the airline must advise the coordinator, and return any slots it knows it will not use. Unwanted slots must be returned no later than 15 January for the next Northern Summer season and no later than 15 August for the next Northern Winter season.
    (source: IATA Worldwide Slot Guidelines)

  • Historics Baseline Date

    The series of slots held by an airline on 31 January for the following Summer scheduling period, or on 31 August for the following Winter scheduling period, is used as the basis for determining eligibility for historic precedence.
    All cancellations made after the Historics Baseline Date are considered as non-utilization of the series of slots in the 80% usage calculation, unless the non-utilization is justified for any of the following reasons:
    Interruption of the air services of the airline due to unforeseeable and unavoidable causes outside the airline’s control, for example a closure of an airport or airspace or severe weather; or
    Action intended to affect these services that prevents the airline from carrying out operations as planned, for example, industrial action or strikes.
    (source: IATA Worldwide Slot Guidelines)