An aircraft control device calculates trajectories of multiple aircraft that is member of a flight by use of a method such as Direct Collocation with Nonlinear Programming (DCNLP), in which an optimal solution is obtained by discretizing continuous variables. Nodes indicating the trajectory are calculated and set by substituting a discretized control variable of the aircraft into an aircraft equation of motion, or by use of other methods. Instead of calculating the trajectory of the aircraft as a continuous problem, discretisation reduces the calculation amount and time required for the trajectory calculation. The aircraft control device then determines, from among trajectories satisfying constraints corresponding to the role of the aircraft, an optimal trajectory based on an evaluation value obtained by an objective function corresponding to the role. Accordingly, the aircraft control device can calculate a more optimal trajectory corresponding to the role of the aircraft in a shorter time.
