Airports around the world are facing a steady growth in air traffic. Future demand forecasts show a doubling of air travelers over the next two decades. Based on this level of growth, many airports are dealing with capacity bottlenecks, especially during peak times, creating pressure on infrastructure and leading to congestion and delays. Since building airport expansions is being outpaced by growing airline demand, the actual capacity of an airport's infrastructure heavily depends on the efficient utilization of its resources.
In particular, large international airports are exposed to issues concerning infrastructure capacity as several hundreds of flights must be handled each day. It comes as no surprise that the assignment of aircraft (i.e. flights) to stands defines a scheduling problem that needs to be executed carefully in order to accommodate the continuous growth of air traffic. However, there are numerous constraints that need to be taken into account as flights and stands have different specifications and not all flights can be assigned to all stands. Typical hard constraints include the compatibility of flights and stands, slack times between two consecutive flights and conflicts between adjacent stands. Whereas hard constraints must be strictly met in order to deliver a feasible solution, soft constraints are used to define objectives which are applied depending on the airport's emphasis.
Generally, the stand assignment must be decent for the airport's operations and convenient to airlines and passengers. Therefore, airports may pursue several, often competing objectives. One main focus is to assign as many flights as possible to on-pier stands instead of remote stands in order to increase airport revenue and customer satisfaction. When flights are assigned to remote stands, passengers have to be transferred to and from the terminal by bus. This not only increases operational costs and passenger transfer times but also decreases airport revenues given that airlines usually pay lower fees for remote stands. In some cases, aircraft are towed between stands to realize a better utilization of piers. However, since towing procedures are both costly and a safety issue, airports aim to keep them at a minimum. Another main focus is the adherence to airline preferences. Airlines require specific facilities only available at certain stands, resulting in the need to respond effectively to customers' requirements.
The attainment of plan stability with respect to disruptions, especially flight delays and cancellations, is a further non-trivial task. The goal is to maximize robustness by scheduling buffer times between stand usages. If a flight departs late from its assigned stand, buffer times can compensate for delays without having to adjust the stand assignment. If buffer times are not included, a knock-on effect on the following flights that were assigned to the same stand is likely to happen. Since disruptions at airports are part of everyday life, operators need to be able to quickly handle changes in the plan without having to reschedule the stand assignment completely.
When the number of flight movements further increases, the deployment of a software solution can help to manage growth without compromise. INFORM's Stands Solution supports the long-, medium- and short-term planning of aircraft stands, which allows the creation of a plan with maximum use of stands in compliance with all hard and applicable soft constraints. The adherence to preference rules can be measured to evaluate the result, and optimization goals can be weighed against each other (e.g. robustness vs. gate usage, airline preferences vs. number of tows). On the day of operation, the validity of the stand assignment is permanently assessed which enables a quick reaction to potential conflicts in the operation. Moreover, a built-in decision support makes reassigning stands a simple process. Presuming the complexity of the stand assignment increases non-linear with the number of constraints, automation of either the complete or part of the stand assignment becomes an important competitive factor for smooth airport operations.
On the basis of an intelligent and optimized stand assignment, airports can reduce delays and save considerable cost while increasing airport revenues and convenience to airlines and passengers.
Read more about our Stands Solution here.