Abstract: An early warning system for a tractor operator engaged in towing or pushing an aircraft includes two ultrasonic sensors that are used to create a detection area in which the aircraft should be present when the steering angle is well within a safe range. When one of the detectors fails to detect the presence of the aircraft, then the operator is alerted, before over steering can occur, in order that corrective action can be undertaken. Accordingly, complex distance-measuring algorithms can be avoided as can the requirement that an aircraft fuselage have a specially modified detection region.