FAA Office of Aerospace Medicine 
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-26/15

Title and Subtitle: Benchmarking Fatigue in United States Helicopter Air Ambulance Pilots

Report Date: 2/6/2026

Authors: Hannah M. Baumgartner, Justin Durham, Teena Sanders, Sarah E. Westrick,Cassie J. Hilditch

Abstract: 
Helicopter air ambulance (HAA) pilots are exposed to fatigue risk due to on-call and shiftwork operations required for24-hour emergency service. The current field study aimed to provide a benchmark for fatigue in US HAA operations to inform future fatigue management strategies. US HAA pilots working 7-days-on, 7-days-off schedules were invited to participate in a field study. Data collection included 3 days Pre-hitch, a 7-day Duty Period (hitch), and 3 days Post-hitch(recovery) and involved reaction time tests, subjective sleepiness and fatigue ratings, workload ratings, and actigraphy to estimate sleep metrics. Pilots (N = 120, from 21 US HAA companies) working either daytime, nighttime, or mixed(e.g., 3 days followed by 4 nights) schedules completed an initial survey followed by 13 days of data collection during normal operations. The current study found that: (i) half of the HAA pilots surveyed have poor quality sleep; (ii)cumulative fatigue builds across a 7-day hitch, affecting performance on all schedule types; (iii) pilot subjective fatigue and sleepiness ratings remained consistent, even when objective measures of performance worsened; (iv) pilots obtain less sleep during a hitch than on days off on all schedule types, despite taking extra naps during night duties; (v)fatigue accumulates faster across a duty period for night and mixed schedules compared to day schedules; (vi) fatigue accumulated across a hitch persists into recovery days; (vii) circadian disruptions associated with flight requests and subsequent trips operated during periods of low circadian alertness negatively impact performance; and (viii) pilots experience sleep inertia effects (reduced alertness) when woken up by a flight request. Altogether, these results offer the most comprehensive assessment of US HAA pilot fatigue since the introduction of updated HAA regulations in 2014and offer a number of potential fatigue mitigation opportunities for the industry.

Key Words: fatigue, helicopter air ambulance, HEMS, sleep

No. of Pages: 65