Incorrect situation awareness may lead to an overestimation or underestimation of the state of a system, which is referred to as type I and II errors. Decision making might be regarded as the process of transition from the available information domain to the domain of possible solutions, thus depending on the estimated state of a system, the pilot forms his/her judgment and chooses a strategy for further actions. In this paper, a model of error formation in an aeronautical decision making is proposed as a confusion matrix of hypotheses along with an analysis of the two estimation error types. Furthermore, a possibility to quantify the total error of making wrong decisions, depending on the chosen number of the parameters under control is addressed. This determines the existence of a point corresponding to the optimal amount of available information, the threshold of the number of controlled parameters to estimate the condition of a system with a higher degree of accuracy.