Abstract: An aircraft component assembly jig includes: header plates; positioners provided on each of the header plates, each positioner including a receiver that comes into contact with a lower/upper surface of an aircraft component, each positioner causing the receiver to advance and retract; receiver state detectors, that each detects, as control data, a supporting state of a corresponding one of the receivers; and a circuitry. The circuitry compares each of detection values of the control data with a preset reference value to determine whether an equal support state is achieved, the equal support state being a state where all the receivers are equally supporting the aircraft component. If it is determined that the equal support state is not achieved, the circuitry controls an adjustment-requiring positioner among all the positioners to adjust an advancing/retracting position of the receiver of the adjustment-requiring positioner within a design tolerance.