Fairness in the aircraft landing problem

The last few decades a lot of attention has been paid to Collaborative Decision Making (CDM) in Air Traffic Management. A lot of models are proposed in which information of stakeholders (mainly airlines) is used in some way to improve the decision process. When doing this, fairness becomes an important issue. However, it is not always clear what will be considered fair by the airlines involved. In this paper we will use the aircraft landing problem to illustrate various definitions of fairness, that stem from the use of airline preferences. In this problem, a landing order and feasible landing times have to be determined for a set of flights at a runway. The airlines cost and the various definitions of fairness are used as objective for the problem. Local search heuristics are introduced to solve these formulations. Numerical experiments using schedule data from a large European airport are used to evaluate how the fairness definitions and heuristics behave for real life problems. The results show that it is possible to achieve more fairness, while still obtaining considerable cost savings compared to the First Come First Served schedule. The heuristics obtain reductions of up to 26 % in the root mean square deviation of the average cost per airline. The different heuristics show that schedules with different trade-offs between efficiency, cost, delay and fairness can be obtained. Hopefully, these results can be a starting point for discussing the fairness issues related to the introduction of CDM processes among air traffic stakeholders.