Abstract The paper deals with the process of shaping the operational effectiveness of military aircraft under some specific circumstances, i.e. while flying on missions. The term ‘effectiveness’ has been assumed to mean the probability of accomplishing an air mission by one of the aeronautical system’s components, i.e. the aircraft together with its pilot. There is a chance to improve the effectiveness, or make it worse, in subsequent flights, depending on how the maintenance support function. The correct operation and maintenance of the system’s components should provide that the following condition is satisfied: * Pk ≥ P , where Pk - effectiveness in the k-th flight, and P* - the lower demanded limit of effectiveness. The Authors drew their inspiration for this paper from publication [2].