Allocation takes place per season

The operational year is divided into a winter season (W) that coincides with the period that it is winter time and a summer season (S) that coincides with the period that it is summer time. The seasonal changes are therefore the end of March and the end of October.  The seasons are indicated with the year digit.  For instance for a summer season S21 and a winter season starting in 2021 W21.

The Slot Historic List (SHL) contains slots with historic rights

The allocation of a season starts with the preparation of the SHL. The SHL contains the series of slots for who have complied with the “use it or lose it” rule.  The slots with historic rights included in the SHL are reallocated to the airline when it requests them for the next equivalent season.

The capacity limit is declared by the airport

The capacity limit is announced twice a year by the airport in the capacity declaration. The capacity limit indicates the maximum available capacity for the allocation process. It may be that, prior to the start of a summer season, unused capacity  from the winter is transferred to the summer. Then the capacity limit changes and slots from the waiting list can be issued.

The seasonal allocation starts with the Initial Submission and ends with the Historic Baseline Date

After the applications have been submitted by the airlines, the seasonal allocation takes place. The first allocation is the Slot Allocation List (SAL).  At SAL also the waitlist (WL) of not allocated slots is made.  After SAL airlines return series they don’t expect to operate (Series Return Deadline (SRD)). The final allocation after all reconciliations ends in the Historic Baseline Date (HBD). The HBD is the reference point for determining the SHL for the next equivalent season.

During the season the allocated slots and waitlist are kept actual

Approximately 8 weeks after HBD, the season will actually start (SoS). Changes in the timetables of the airlines are processed in the slotportfolio and waitlist during the season.  At the end of the season (EoS), it can be measured how many slots are ultimately allocated, including ad hoc allocations and cancellations and how many flight movements have actually taken place.

In collaboration with the airlines ACNL monitors continuously the portfolio of slots and the waitlist

Numerous organizations use slotdata, like airports, ground handlers, air navigation service providers.  Accuracy of the slotportfolio enables efficient use of airport capacity.  ACNL monitors and has dialogues with airlines about the management of the slotportfolio and the waitlist.