The steady growth of air traffic volumes and the subsequent increase of congestion at major airports require airports to increase their operational efficiency. Inefficient or the absence of gate reassignment models increase the possibility and occurrence of gate blockage and at the same time reduce the comfort of passengers as they often receive the notice that they have to wait for their assigned gate to become available. This thesis describes a model to optimally reallocate flights to available gates on the actual day of operation for a large airport, such as Amsterdam Airport Schiphol (AMS). It takes into account the scheduled arrival time of a flight for the initial assignment, during daily operation the model updates the scheduled arrival time with the estimated arrival time as soon as the flight is enroute. The proposed model allows the user to do a trade-off between delaying, gate changing and remote handling of flights. The sliding time window has shown to reduce the number of gate changes required during daily operation in order to mitigate gate conflicts. Validation of the model with data obtained from AAS showed that the approach is feasible for real world application and that it improves the operational efficiency of the airport.