For a long time, the aim of safety science has been to further improve safety through more extensive analysis methods (address more factors, with increasingly complex causality models). However, recent research has uncovered how the application of even very advanced methods are subjects to the same pressures of reality of work, as other work tasks, and may therefore also have incidents, where all issues are not examined with equal thoroughness, and not implemented with the same enthusiasm. Some of these performance shaping factors may be systemic, affecting many investigations, resulting in investigation "blind spots". This can facilitate the build-up of latent risk conditions in otherwise ultra-safe organizations, resulting in what is in the literature called a man-made disaster (or, less dramatically, a man-made incident). In this paper, we present an approach to uncovering "blind spots" in investigation processes, describing how it was applied at an Air Navigation Service provider.