In a military context, the process of planning operations involves the assessment of the situation, the generation of Courses of Action (COAs), and their evaluation according to significant points of view, in order to select the course of action that represents the best possible compromise. Since several conflicting and quite incommensurable criteria need to be considered and balanced to make wise decisions, MultiCriterion Decision Aid (MCDA) has been used to develop decision support systems. Defence Research and Development Canada – Valcartier (DRDC Valcartier) has developed an advisor tool to assist the Air Operation Centre staff in managing events and their related COAs, as well as prioritizing these COAs according to different evaluation criteria by means of a MCDA procedure. Following this development, an investigation has been conducted to provide this decision support system with explanation facilities. This paper describes the suggested approach for the automated generation of explanations of a ranking proposed by a decision support system based on a MultiCriterion Aggregation Procedure (MCAP).