O'connor P, Cowan S, Alton J. A comparison of leading and lagging indicators of safety in naval aviation. Aviat Space Environ Med 2010; 81:677–82. Background: The purpose of this paper is to examine the results of two different methods of identifying human factors safety concerns in U.S. Naval aviation. In both studies, the information was collected using the Department of Defense Human Factors Analysis and Classification System (DoD-HFACS). Methods: In the first study, aviation mishap data (a lagging indictor) was obtained on 47 F/A-18 and 16 H-60 mishaps. In the second study, the responses of 68 squadrons to a survey regarding the human factors issues that they considered to be of the greatest safety concern were examined (a leading indicator). Results: First study results revealed that skill-based errors were the most commonly cited factors for both F/A-18 and H-60 mishaps (70.2% and 81.3%, respectively). More specifically, the most commonly used nanocodes were ‘over control/under control’ (27.7% and 56.3%, respectively), ‘breakdown in visual scan’ (27.7% and 12.5%, respectively), and ‘procedural errors’ (23.4% and 37.6%, respectively). The second study identified that the main concern of F/A-18 and H-60 aviators was workload and operational tempo (identified by 85% of squadrons). Discussion: It can be concluded that the nanocodes that were most commonly used to classify the causes of past mishaps were not identified as major concerns by the squadrons who responded to the survey. The findings from these studies emphasize the importance of examining a number of performance metrics to ensure that effective measures are being taken to improve safety.