Characterizing Pilot Fatigue During Circadian-Disrupted Short-Haul Aviation Operations

Short-haul aviation pilots often operate irregular schedules that encroach on the biological night and disrupt sleep, alertness, fatigue, and cognitive performance, posing a potential safety risk. Regulatory limits and industry practices exist to mitigate such impairments, but few studies have examined the impact of circadian-disrupted schedules.

Commercial passenger pilots from four U.S. airlines collected data during, and 1-3 d before and after, two trip types: one with circadian disruption (i.e., ≥1 duty day encroaching on the biological night); and one without. Sleep was measured using actigraphy and sleep logs. Subjects completed a 5-min psychomotor vigilance task, Karolinska Sleepiness Scale, and Samn-Perelli fatigue scale 3x/day on days off and after waking, pre-duty, at top-of-descent for each flight, post-duty, and before bed on duty days. We compared outcomes with mixed-effects models adjusted for multiple comparisons.

Subjects (N = 159) provided valid data for analysis. We found small but significant differences (all d values <0.30) between circadian-disrupted and nondisrupted trips, with greater sleepiness (4.77 ± 2.16 vs. 4.43 ± 2.11), greater fatigue (3.64 ± 1.38 vs. 3.37 ± 1.34), slower response speed (1000/reaction time; 3.86 ± 0.63 vs. 3.94 ± 0.61), and less total daily sleep time (6.28 ± 1.73 h vs. 6.75 ± 1.28 h) during the circadian-disrupted trips.

Our findings suggest that there is a small but significant reduction in alertness and performance when working during the biological night that remains, even when prescriptive limitations and existing airline mitigations are in place. Flynn-Evans EE, Bathurst N, Pradhan S, Gregory KB, Barger LK, Lamp ACM, Glaros Z, Arsintescu L, Jansen RA, Baumgartner HM, Nesthus TE, Hilditch CJ. Characterizing pilot fatigue during circadian-disrupted short-haul aviation operations. Aerosp Med Hum Perform. 2026; 97(8):607-617.