A control unit of an aircraft includes a computer that predicts the current position of a wingman aircraft based on a temporal change in wingman-aircraft position information indicating the position of the wingman aircraft; an antenna selector that selects, from among multiple antennas, an antenna with which the elongation φt with respect to the center axis of the antenna at the predicted current position of the wingman aircraft predicted by the computer falls within a coverage angle θ; and a beam controller that executes communication with the wingman aircraft via the antenna selected by the antenna selector. Thus, the control unit of the aircraft can select an optimal antenna for communication with the wingman aircraft from among the multiple antennas.