Provided is an air traffic control assistance system whereby it is possible to display the reliability of an avoidance recommendation over time in a manner which is easily understood by an air traffic controller. For each combination of link information of an aircraft of interest and link information of an aircraft in the vicinity thereof, a graphic identification unit identifies a graphic which represents a prescribed range which is defined by the aircraft in the vicinity thereof, in a plane which includes a three-dimensional vector which is represented by the link information of the aircraft of interest and which is perpendicular to the x-y plane. When transforming a two-dimensional vector in an x-y plane from one fix of the aircraft of interest to the next fix to align in order along the x-axis, a transform matrix computation unit computes, for each two-dimensional vector, a transform matrix which represents a transform from a plane which contains the two-dimensional vector and is perpendicular to the x-y plane to a plane which is defined by the x-axis and a time axis. A display processing unit transforms the graphic, and displays a line which joins the fix and a point which is determined by the time whereat the aircraft of interest transects the fix, and the transformed graphic.