Abstract: A method that enables an aircraft to determine an optimal terrain following, terrain avoidance, or threat avoidance trajectory over terrain, thereby reducing its exposure and increasing its survivability. A grid of discrete terrain points corresponding to the terrain above which the aircraft is to fly is formed. Each point has a cost that is function of predetermined criteria. A cost is assigned to each of the points that is representative of the cost to get to the point based upon the predetermined criteria. A terminal point is selected that is a point that must be flown through at the end of the trajectory over the terrain, or in order to clear an obstacle in the flight path of the aircraft. A series of paths is computed through the terrain points to a selected terminal point, taking into account the aircraft's maneuvering capability and current attitude.