The increasing number of flight operations, and the resulting increased likelihood of adverse situations, intensifies the need for research into aspects of aircraft reliability. This article is devoted to the reliability of selected assemblies of the PZL M28 Bryza aircraft, widely used in military and civil aviation. The article presents the research object, the PZL M28 Bryza aircraft, and the research methodology to assess the reliability of its key assemblies. The research focuses on analyzing the failure rate of such assemblies as the propulsion system, airframe, radioelectronic devices and on-board systems, using in-service data. The results provide a better understanding of the critical aspects affecting the reliability of the PZL M28 Bryza aircraft, which is important for improving the safety and efficiency of flight operations conducted.