Introduction. Composite materials are the main way to reduce the weight of the aircraft structure and improve its flight performance. Methods of non-destructive testing enable to assess the technical condition of composite materials, as well as to determine stress concentrators in them to make a decision on the further operation of this control object. The paper presents an analysis of the use of composite materials in the aircraft design and ways to improve their flight performance through the application of composites. An acoustic-emission method for assessing crack resistance based on invariants was described.   The study aimed at increasing the accuracy and efficiency of assessing the crack resistance of aircraft structures made of composite materials through the use of the acoustic emission method of non-destructive testing.   Materials and Methods. The nomenclature of composite materials used in aircraft was given, and their physical and mechanical properties were compared. The acoustic emission method of non-destructive testing of composite materials based on invariant ratios was used.   Results. A method for assessing the crack resistance of primary structural elements based on the invariants of acoustic emission processes, and a program apparatus complex based on it has been developed.   Discussion and Conclusions. The results obtained can be used to determine the strength characteristics of composite materials by the acoustic emission method of non-destructive testing to assess the technical condition of primary structural elements in mechanical engineering, shipbuilding, and aircraft construction. The paper is recommended to researchers involved in the development of aircraft.