Article Info AbstractKeywords: Airport Logistics Check-in Counter Allocation Problem Optimization Models Simulation This paper presents a new methodology to optimize the Airport Check-in Counter Allocation Problem. The methodology combines optimization, simulation and adjacent resource scheduling and aims to determine the optimal number, location and schedule of check-in desks to open for departing flights, such that operational costs are minimized and a given service level is ensured. The methodology is composed of three steps.Step 1 uses optimization models to determine the optimal number of desks.Step 2 uses simulation to assess if the first step results meet the overall service level.Step 3 uses an optimization model to enforce the adjacent constraint. The paper focus then onStep 1, to which we present two new optimization models for common and dedicated check-in systems which include a service level constraint. Finally, these models are applied to a case study with actual data. We conclude the best time interval length should be 30 minutes or less and, as expected, the dedicated system requires, in general, more desks than the common system. Additionally, the results demonstrate the accuracy of the models to reach the trade-off between the operational costs and a given service level.