Time-of-Day Distribution and Human Factors in Recent General Aviation Accidents and Serious Incidents in Türkiye

Human factors are important contributors to general aviation (GA) accidents and serious incidents; however, the potential role of time of day, fatigue, and individual chronotype in GA occurrences remains insufficiently described. This study primarily aimed to provide a descriptive characterization of the temporal distribution and human-factor involvement of these occurrences rather than to test causal circadian mechanisms. This cross-sectional study analyzed GA accident and serious incident reports from Türkiye (2018–2025) publicly available on the Transportation Safety Investigation Center website, of which 33 met the inclusion criteria. Variables extracted from each report included operation type, flight phase, reported fatigue, medical contribution, operational human factors, and local occurrence time. Events were grouped into four predefined time-of-day blocks and their distribution was assessed using a chi-square goodness-of-fit test. Among the 33 included events, 11 were accidents and 22 serious incidents. Most occurred during training operations (25/33, 75.8%) and during the landing phase (19/33, 57.6%). A focused narrative review of the final reports showed that 32 of the 33 included events (97.0%) involved operational errors or violations attributable to personnel actions or decision-making. The distribution across the four time-of-day blocks was statistically non-uniform (χ²(3)=12.45, p=0.006), with the highest concentration between 10:00 and 13:59 (17/33, 51.5%). Fatigue was explicitly reported in only one event, and no medical cause was identified as a contributing factor. The observed late-morning concentration should be interpreted cautiously as exposure data were not available. Although this study does not establish a causal relationship between circadian timing, chronotype, and GA occurrences, chronotype-schedule mismatch may be considered a hypothesis for future research.