Airport Gate Assignment A Hybrid Model and Implementation

With the rapid development of airlines, airports today become much busier and more complicated than previous days. During airlines daily operations, assigning the available gates to the arriving aircrafts based on the fixed schedule is a very important issue, which motivates researchers to study and solve Airport Gate Assignment Problems (AGAP) with all kinds of state-of-the-art combinatorial optimization techniques. In this paper, we study the AGAP and propose a novel hybrid mathematical model based on the method of constraint programming and 0 - 1 mixed-integer programming. With the objective to minimize the number of gate conflicts of any two adjacent aircrafts assigned to the same gate, we build a mathematical model with logical constraints and the binary constraints. For practical considerations, the potential objective of the model is also to minimize the number of gates that airlines must lease or purchase in order to run their business smoothly. We implement the model in the Optimization Programming Language (OPL) and carry out empirical studies with the data obtained from online timetable of Continental Airlines, Houston Gorge Bush Intercontinental Airport IAH, which demonstrate that our model can provide an efficient evaluation criteria for the airline companies to estimate the efficiency of their current gate assignments.

💡 Research Summary

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The paper addresses the increasingly complex problem of assigning airport gates to arriving and departing aircraft, a task that has become critical as airline traffic grows. While a substantial body of literature has tackled the Airport Gate Assignment Problem (AGAP) using various combinatorial optimization techniques—such as linear and mixed‑integer programming, genetic algorithms, tabu search, simulated annealing, and stochastic programming—most studies focus on a single objective (e.g., minimizing passenger walking distance) or treat gate conflicts only implicitly.

In contrast, the authors propose a novel hybrid mathematical model that integrates Constraint Programming (CP) with 0‑1 Mixed‑Integer Programming (MIP). This combination leverages the logical expressiveness of CP (to enforce “one‑gate‑per‑aircraft” and “no simultaneous use of a gate”) together with the powerful binary decision variables of MIP (to select which gate each aircraft occupies). The model defines binary variables (x_{i,k}) (aircraft (i) assigned to gate (k)) and auxiliary variables (y_{i,j}) that become 1 when two aircraft share the same gate. A buffer time (b) is introduced to enlarge the effective occupancy interval of each aircraft to (