Efficacy of Fatigue Countermeasures on Cognitive Performance and Operational Safety in Military Pilots: A Systematic Review.

Fatigue poses a significant risk to operational safety and performance in military aviation due to irregular schedules, night operations, and deployment environments. A range of countermeasures is employed, but their efficacy, specifically for military pilots, requires further exploration. This systematic review evaluated the current evidence on the effectiveness of behavioral, operational, and pharmacological fatigue countermeasures specifically for military pilots, to inform practice and policy. A systematic search of PubMed, Scopus, ScienceDirect, Research Gate, Cochrane Library, Google Scholar, and Web of Science was conducted for studies published between 2014 and 2025. Eligible studies included randomized controlled trials, non-randomized trials, and observational studies involving active-duty military pilots or aircrew, assessing any fatigue countermeasure against alertness, cognitive performance, or operational safety outcomes. Seven studies were included. Pharmacological interventions, particularly caffeine and modafinil, were the most effective short-term countermeasures, improving vigilance, reaction time, and performance during extended wakefulness. However, their efficacy was moderated by individual factors, such as innate fatigue vulnerability and sleep quality, and neither fully restored baseline performance under conditions of severe sleep deprivation (e.g., >27 hours awake). Evidence for behavioral countermeasures, such as habitual video gaming, was limited and showed no protective effect against cognitive fatigue. Technological approaches, like eye-tracking for real-time cognitive load monitoring, showed promise but require further validation in operational settings. This review shows that pharmacological strategies currently provide the most evidence-based approach for mitigating acute fatigue in military pilots. However, an over-reliance on stimulants is insufficient. Future fatigue management requires an integrated, personalized system combining real-time monitoring, validated countermeasures (including novel approaches and sleep-focused strategies), and a systemic cultural shift that prioritizes sleep as a critical component of operational readiness. Further high-fidelity research in real-world operational environments is essential.