In the present invention, an aircraft control device computes the trajectories of a plurality of formation-flying aircraft using a calculation method; e.g., direct collocation with nonlinear programming (DCNLP), in which the optimal solution is obtained by discretizing continuous variables. Trajectory-indicating nodes are computed and set by plugging discretized aircraft control variables into an aircraft motion equation or by using another method. Using discretization to address aircraft trajectories reduces complexity and allows the trajectories to computed more rapidly than with computations involving chronologically contiguous aircraft trajectories. The aircraft control device determines the optimal trajectory, among trajectories that comply with constraints corresponding to the role of the aircraft, on the basis of an assessment value obtained by an objective function corresponding with the role. Accordingly, the aircraft control device is capable of performing computations more rapidly on more suitable
