A surveillance system detects potential hazards and alerts the pilot to them. The alerts can be modified to indicate proximity to the predicted path of the aircraft. An autopilot receives instructions from a flight management system (FMS) regarding a planned path and is subject to constraints preempting the planned path. The surveillance system selects which of the planned and a constrained path will be followed for alerting and hazard coding purposes. Means are disclosed to determine when the constrained path will be followed by comparing the current position of an aircraft, the planned path, and the constraint data. Current positions exceeding the tolerance cause the surveillance system to select the planned path as the future path to be followed. If initiation of a constraint has been detected and the current position is within the tolerance, the surveillance system selects the constrained path as the future path.