ABSTRACT
Objectives/Introduction: Fatigue in airline pilots can arise from multiple sources, including human factors, environmental factors such as weather or noise, busy schedules, unforeseen day-of-operation changes like flight delays, or COVID-related precautions like maskwearing. Fatigue from multiple sources creates a compound safety risk. Job experience or sleep debt may affect how individual pilots experience fatigue during operations. Neither multi-source fatigue factors nor the role of individual differences been examined in the context in medium-haul flights. Method(s): Pilots working medium-haul rosters for a major European airline were asked to rank the level of fatigue they experience from 30 separate factors across five domains: (1) Human;(2) Environmental;(3) Scheduling;(4) Day-of-Operation;and (5) COVID-related. Pilots were also asked to provide experience information-total flight h, age, rank-and to indicate their normal sleep duration and minimum sleep need to perform. Sleep debt was computed as normal sleep - minimum sleep need. Rank differences in flight h, age, and sleep debt were examined using t-tests. One-way analysis of variance (ANOVA) was used to examine the role of experience and sleep debt on overall fatigue, as well as fatigue for each fatigue sub-domain. Result(s): N = 135 medium-haul pilots (64 Captains;71 First Officers (FO);mean age: 43 +/- 2 years) completed the online survey. Pilots reported needing a minimum of 5.5 +/- 1 h of sleep;sleep debt did not differ by rank (t = 1.22;p = 0.22). Captains were ~11 years older than FOs (t = 11.28;p < 0.001) and had 7801 +/- 860 more flight h (t = 17.88;p < 0.001). Captains reported more human factors (F = 9.53;p = 0.002), environment (F = 9.32;p = 0.003), day-of-operation (F = 7.48;p < 0.001), and overall fatigue (t = 3.20, p = 0.002) compared to FOs. Greater sleep debt predicted greater human factors (F = 4.20;p = 0.042), scheduling (F = 8.95;p = 0.003), and day-of-operation fatigue (all p <= 0.04). COVID fatigue was not related to experience or sleep debt (all p > 0.09). Conclusion(s): Captains may experience more fatigue than FOs, particularly in domains related to executive decision-making (human, environment, day-of-operation). Pilots with greater sleep debt may experience more fatigue related to circadian (scheduling, day-ofoperation) or interpersonal factors (human) regardless of rank. COVID-related fatigue is not predicted by sleep or rank. These findings provide targets for fatigue mitigation due to compound risk.