The reliability of a technical system, and especially the reliability of a complex hierarchy of technical local segments, some of which are program and have a close connection with system elements of the upper levels of the hierarchy today has many concepts and meanings, to integrate which for a real understanding of the situation is extremely difficult, and, in most cases, virtually impossible.Recently, there have been developments that suggest to single out from all local fragments of the integrated reliability of such a system some elements that determine the reliability of the most dangerous elements of this system, to some extent and at the expense of the integrated reliability of the entire complex.For each individual fault - from a light bulb burnout to engine failure - their impact on the aircraft as a whole, its controllability and aerodynamics was modeled. As a result of this analysis, the engineers were given a tree of mutually influencing faults, from which they could understand which parts should be changed.