Fatigue Exposure in the Context of Nighttime Airline Operations

Introduction: A. Introduction Managing crew fatigue is a critical aspect of aviation safety, particularly in the context of night duties. Following changes in fatigue risk requirements (EU2023/023/R) by the European Aviation Safety Agency (EASA), a leading airline operating medium- and long-haul flights conducted scientific research investigating its crews’ exposure to fatigue risk. A key component of this regulation is the classification of nighttime flight duty periods (FDPs) based on their potential to induce fatigue. EASA distinguishes three subtypes: FDPs starting between 02:00 and 04:59, FDPs starting before 02:00 and ending between 02:00 and 05:59, and FDPs starting before 02:00 and ending after 05:59. The effects of these nighttime FDPs on fatigue levels among crews were analyzed. By assessing fatigue exposure and identifying contributing factors, the study aimed at supporting regulatory compliant fatigue risk management. The objectives were 3-fold: - To identify currently implemented fatigue risk management measures; - To diagnose fatigue risk exposure levels among crews; - To support the airline in managing fatigue risk.

Methods: To capture an accurate view of crew fatigue, the project was based on scientific principles, establishing an objective research methodology performed in multiple phases. First, current measures in place were identified through the analysis of documentation and rosters using scientific criteria. Additionally, collective interviews were organized with crews. Associated research hypotheses were defined based on the results of this review. Subsequently, a detailed fatigue data collection was performed. Data of 72 participants were gathered during actual operations to identify operational factors contributing to crew fatigue, allowing for fatigue risk management tailored to the operations.

Results: Overall, 10.4% of reported FDPs (daytime and nighttime) showed critical fatigue levels, i.e., values exceeding 5 on the Samn-Perelli scale. Workload was identified as a key factor influencing fatigue. Delays and challenging passengers correlated with increased fatigue levels. The types of nighttime FDPs do not impact critical fatigue levels. While long-hauls showed higher fatigue levels compared with medium-hauls, mixing operations do not affect fatigue. No other factors related to schedules were found to significantly affect fatigue levels.

Conclusion: By integrating scientific assessment methods, this study provided a foundation for enhancing fatigue risk management processes in compliance with regulations. Workload, delays, and challenging passengers were identified as significant contributors to fatigue. This data-driven fatigue risk management allows the airline to minimize fatigue risk while ensuring regulatory compliance. Moving forward, continued fatigue monitoring, crew feedback integration, and periodic assessments remain essential in fatigue risk management. Future research must explore the effectiveness of countermeasures and investigate fatigue on longitudinal levels.

Publication History

Article published online:
08 October 2025