# Ferry Scheduling Optimization Considering Arrival Time Uncertainty and In-Place Time Differences
## 1 Introduction  
In large hub airports, aircraft stands can be categorized into two types, the near parking stand and the remote. The nearby positions are fully equipped with all kinds of support equipment, including the power supply, corridor bridges, refueling pipelines, water supply and drainage pipelines. Remote positions need to rely on ground support vehicles, including power supply vehicles, stepladder vehicles, ferries and refueler trucks. With the increase in flights at the airport, it is difficult to continuously improve the utilization rate of the nearby parking stands. More and more flights will be parked at the remote parking stands, which will gradually increase the demand for ground support vehicles. Meanwhile, due to the influence of weather, airspace control, passenger behavior and other factors, it is unavoidable that there are deviations between the actual arrival and departure times of flights and the planned times. At present, the basic information that ground support resource scheduling relies on is the estimated flight arrival and departure times and the information returned from the scene. The lag and one-sidedness of the information have a great impact on the decision making related to ground support resource scheduling. Therefore, the punctuality of flights is the main factor affecting the utilization efficiency of ground support resources. Under the uncertainty of flight arrival and departure times, the rational allocation and effective utilization of ground support resources become more important. The flight ground support process is a service structure that is temporal and mutually exclusive. [PERSON] et al. [1] defined the ground support process as a resource-constrainedproject scheduling problem (RCPSP) and proposed an evolutionary algorithm to solve it. Limited by computational efficiency, vehicle route planning with time windows (VRPTW) has progressively become a major approach to studying the problem of scheduling ground support resources. Concerning the centralized ground support resource scheduling problem, [PERSON] et al. [2] decomposed the original problem. A heuristic was designed to solve each subproblem. In some studies, the flight transit process was defined as a whole. The specific scheduling of the various types of supported services of the transit process was not considered, including in [3; 4]. The results of both studies showed that there are two factors affecting the punctuality of flight departures. They are the length of flight transit time and the efficiency of ground support services. To solve the airside scheduling problem at airports, [PERSON] [5] and [PERSON] et al. [6] conducted research in two distinct directions. The former proposed a multi-level rolling scheduling framework for the support resource scheduling problem under flight arrival uncertainty. The upper layer was a dynamic demand model, which forecasts the demand under the influence of stochastic factors. The middle layer was a resource planning model. The lower layer was a task scheduling model. The latter started from a horizontal perspective. Researchers proposed a multi-objective integrated optimization problem by considering the lack of information sharing at all stages. They solved multi-module problems including runway scheduling, flight taxiing and ground resource scheduling through a joint scheduling method. The flight transit process is also complex. In actual operation and management, different types of resources are divided into different business offices. Different support resources have a high degree of independence in management. Therefore, most of the studies on the scheduling problem of ground support resources focus on the co-scheduling of a small number of types of resources [7; 8] and single-type resource scheduling [9; 10]. The combination of resource types in multi-resource co-scheduling problems has a different impact on the research methodology. [PERSON] et al. [11] investigated the problem of cooperative scheduling of the ferry and refueler.