A literature review, which was conducted during the research project “Measuring Safety in Aviation – Developing Metrics for Safety Management Systems”, identified several problems and challenges regarding safety performance metrics in aviation. The findings from this review were used to create a framework for interviewing 13 companies in order to explore how safety performance is measured in the industry. The results from the surveys showed a wide variety of approaches for assessing the level of safety. The companies encounter and/or recognise problematic areas in practice when implementing their safety management. The findings from the literature review are partially confirmed and it seems that the current ways of measuring safety performance are not as straight forward as it might be assumed. Further research is recommended to explore alternative methods for measuring aviation safety performance.