A recent development in the field of aircraft structural health monitoring is active structural health monitoring based on ultrasonic phased array. Based on existing applications of ultrasonic phased array technology for single damage localization, this paper studies multi-damage monitoring in the aircraft structures. Multi-damage and multi-direction scanning can be achieved by controlling the time delay in order to control wave direction. Experiments are conducted on an aluminum plate. By comparing the damage reflection signals before and after a time delay of different angles and their synthesized signals, it can be proved that delay-superposition of the ultrasonic phased array can effectively increase the multi-damage signal energy, and reduce the signal energy where there is no damage. This improves the signal to noise ratio and demonstrates high accuracy for multiple damage identification.