This paper proposes an optimization model for the integrated aircraft flight scheduling and routing problem, which allows a simultaneous determination of the departure time of each flight trip and assignment of a set of aircraft located at different airports to perform all flight trips. The proposed model envisages that each flight trip is covered by its own particular aircraft type or a larger airplane. Further, departure and arrival times of each flight trip are within a flexible time window in its aircraft's route and origin/destination airports, and the number of airplanes firstly distributed in the base airports is fully accounted for in the model. The model not only can effectively minimize weighted operation costs for the number of a...