This article, based on the analysis and the theoretical approaches of the subject area "Design of aircraft at the sketch stage" proposed a method of aircraft design, which allows mathematically sufficiently effective implementation of the process of aircraft construction, on the example of aircraft using an ontological approach. The approach allows us to identify ways to formalize the two main situations that occur in the design of aircraft: sequential complication and refinement (descending design) and consistent simplification (ascending design). The proposed technology allows to significantly reducing the total design time of the aircraft through the use of several levels of model decomposition.
 The application of the ontological approach facilitates the design process, allows solving the main tasks of modern design at different stages of aircraft creation, to coordinate the parallel work of designers on the project.
 The main advantages of using the ontology design of the developed aircraft are:
 1) effective compact presentation of the knowledge system of the subject area "Design of aircraft" on the basis of modern information technologies (specification and conceptualization);
 2) search for information in the system of knowledge of the obtained ontology (obtaining reference and educational information);
 3) formulation and solution of the necessary applied tasks within the given subject area (tasks of weight design, centering of the aircraft);
 4) development of the system and acquisition of new knowledge or streamlining of existing ones, verification of their consistency, correction of the aircraft design tree.