Factors associated with in-flight G-induced loss of consciousness (G-LOC) in military aircrew

Introduction G-induced loss of consciousness (G-LOC) remains a significant hazard in high-performance aviation. Although protective equipment and anti-G straining manoeuvres improve tolerance to high +Gz acceleration, individual physiological and operational factors may influence susceptibility to G-LOC during flight. The aim of this study was to characterise in-flight G-LOC cases and to identify potential factors associated with these events. Methods This retrospective case-control study analysed all in-flight G-LOC events reported among Israeli Air Force cadets and fighter aircrew between 2015 and 2025. For each case, four controls matched for age and squadron were randomly selected without a history of G-LOC. Variables included anthropometric characteristics, resting blood pressure, operational role during the manoeuvre, flight training stage, G-levels at the time of G-LOC, incapacitation duration and preceding symptoms. Results Fifteen in-flight G-LOC events occurring in 13 individuals were identified. The mean age at the time of the event was 23.4±5.6 years. The mean incapacitation duration was 19.6±9.9 s. Visual symptoms preceded loss of consciousness in 73% of events. G-LOC cases were significantly taller than matched controls (183.8±6.3 cm vs 176.8±3.3 cm, 95% CI 2.89 to 11.01, p=0.003). Within the G-LOC cohort, higher G-levels at the time of G-LOC were observed during events in which the affected pilot was directly controlling the aircraft. Among cadets, G-level at the time of G-LOC was positively correlated with training stage (Spearman ρ=0.74, p=0.014). Conclusions These findings provide observational data suggesting that anthropometric and operational factors may influence the conditions under which G-LOC occurs during flight.