In recent years, in some cases, the air traffic amount is increasing and a near miss (conflict) between aircrafts occurs. A conflict is a state that two aircrafts travelling at the same altitude approach more closely than a distance set to assure safety (oceanic air traffic control separation).
In the case that occurrence of a conflict is detected in advance, an avoidance proposal of changing the state of an aircraft is generated in order to avoid the conflict. The generation of the avoidance proposal is not limited to one. An air traffic controller selects an avoidance proposal and instructs the aircraft in accordance with the avoidance proposal. One avoidance proposal indicates a change in speed or altitude of one aircraft. Therefore, it can be said that one avoidance proposal corresponds to one aircraft.
Various devices for assisting an air traffic controller have been proposed (for example, refer to patent literature 1 and 2). A device described in PTL 1 generates an avoidance proposal to avoid a conflict and displays respective avoidance proposals in order based on priorities of the avoidance proposals.
A system described in PTL 2 extracts aircrafts existing in a predetermined range and three-dimensionally displays the aircrafts.