We analyzed the characteristics of sustained attention changes in flight crews during exempt and non-exempt flights. Fourteen pilots (aged 30-43 y) participated in this study, with seven involved in each flight type, all of which were intercontinental (China to North America). Pilots completed continuous performance tests (CPT) at the required flight stages without compromising safety while on duty. No significant differences in sleep and sustained attention emerged between the exempt and non-exempt flight crews. Pilots' fatigue was highest in the early morning hours. Their general stability of efficiency increased during the day and decreased at night. Non-exempt flight crews appeared to sacrifice reaction rate to improve accuracy. Exempt crews appeared to increase their test proficiency. The task stability time of the non-exempt flight crews was better than that of the exempt ones. Short-term stability was better for exempt inbound flights rather than for outbound ones. Pilots were more prone to error runs as their total time awake increased, especially on non-exempt flights. The addition of crew members to exempt flights, allowance for more in-flight rest shifts, and over-stop rest on non-exempt flights may alleviate pilot fatigue and preserve alertness.
Keywords: Aviation safety; exempt flight; intercontinental flights; non-exempt flight; pilot fatigue; sustained attention.