The slot is the scheduled time of arrival or departure allocated by a coordinator for an aircraft movement on a specific date at a coordinated airport. For scheduling purposes, the slot is the scheduled time of arrival or departure at the terminal, not the time of landing or takeoff from the runway.
The congestion takes place when the relation between airlines’ demands and airport capacity (supply) gets out balance. Increasing demand for air transport services implies that all facilities at an airport will remain under constant pressure to expand. The problems associated with expansion are complicated by the fact that services must be provided to the maximum possible extent at times when the public requires them. This causes demand peaks in certain seasons of the year, on certain days of a week and at certain hours of a day.
The best way to avoid the congestion is to expand the airport capacity (supply). However, the expansion takes a long time and a lot of money and can not be easily achieved. Without an expansion in capacity or resolution of the problem by other means, an airport becomes congested at certain times. This occurs when the demand for one or more of its limiting components exceeds capacity in a certain time period. To resolve the situation, governments, airport and Air Traffic Control (ATC) authorities and the airlines must continuously find the means to develop the capacity of each of their own systems in order to satisfy public demand.
Over a long period of time, IATA has developed various global guidelines that airlines schedulers, coordinators and facilitators have to follow for schedules coordination and slot allocation. The coordinators and facilitators should act in accordance with those global guidelines as well as local guidelines set for specific airport to balance between the airlines’ demands and available capacity of airports to alleviate the airport congestions.
There are certain constraints at airports such as the capacity of airport facilities, environmental protection and Air Traffic Control (ATC) capacity to assure the safety and regularity of flights. The coordinators adjust the airlines’ demands to satisfy those constraints.
Airlines submit such schedules data as flight number, operation days, arrival time, departure time and aircraft type to schedule coordinators or facilitators by either e-mail or SITA network in a standardized format. When all those data are accumulated, it becomes obvious that the airlines’ demands create several peaks on certain days of a week and at certain hours of a day at congested airport.
The coordinators and facilitators adjust those requests within airport capacity limit as well as Air Traffic Control capacity limit, trying to accommodate requested timings as close as possible according to both IATA guidelines and local ones in a neutral, non-discriminatory and transparent manner. The relationship between airlines’ scheduler, coordinator, facilitators, airport company and airport office can be described in the following diagram.
JSC is in charge of Narita International Airport (NRT), Tokyo International
Airport (Haneda) (HND), Fukuoka Airport (FUK) and Kansai International
Airport (KIX) for level 3 aiport, and New Chitose Airport (CTS) for level
2 airport. Besides these airports, Japan Civil Aviation Bureau (JCAB) is
taking care of Chubu Centrair International Airport (NGO) as level 2 airport.
(note) Kansai International Airport is desingated as level 2 airport until S21.