Summary European regulations restrict the duration of the maximum daily flight duty period for pilots as a function of the duty start time and the number of scheduled flights. However, late duty end times that may include long times awake are not specifically regulated. In this study, fatigue levels in pilots finishing their duty late at night (00:00–01:59 hour) were analysed and compared with pilots starting their duty early (05:00–06:59 hour). Fatigue levels of 40 commercial short‐haul pilots were studied during a total of 188 flight duty periods, of which 87 started early and 22 finished late. Pilots used a small handheld computer to maintain a duty and sleep log, and to indicate fatigue levels immediately after each flight. Sleep logs were checked with actigraphy. Pilots on late‐finishing flight duty periods were more fatigued at the end of their duty than pilots on early‐starting flight duty periods, despite the fact that preceding sleep duration was longer by 1.1 h. Linear mixed‐model regression identified time awake as a preeminent factor predicting fatigue. Workload had a minor effect. Pilots on late‐finishing flight duty periods were awake longer by an average of 5.5 h (6.6 versus 1.1 h) before commencing their duty than pilots who started early in the morning. Late‐finishing flights were associated with long times awake at a time when the circadian system stops promoting alertness, and an increased, previously underestimated fatigue risk. Based on these findings, flight duty limitations should consider not only duty start time, but also the time of the final landing.

Influences of LAeq and number of noise events on daytime performance were small but consistent and significant, stressing the potential public health impact of nocturnal noise exposure.

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The hormone melatonin is currently proposed by some investigators to be an efficient means for decreasing the impairing effects of jet lag. Eight healthy male subjects, aged 20 to 32, underwent a 9-hr advance shift in the isolation facility of our institute during two periods each of 15 days' duration. In a double-blind, crossover design, subjects took either melatonin or placebo at 1800 hr local time for 3 days before the time shift and at 1400 hr for 4 days afterwards. The time shift was simulated on days 7 and 8 by shortening the sleep period by 6 hr and the following wake period by 3 hr. Body temperature was recorded every 90 min, and urine was collected at 3-hr intervals all day and night. Melatonin treatment enhanced the resynchronization speed of some, but not all, hormone and electrolyte excretion rates for several days after the time shift. The adaptation speed of the temperature rhythm significantly increased during one postshift day. In addition, the circadian temperature rhythm had a significantly higher amplitude under melatonin treatment than under placebo after the time displacement. For the placebo group, the rhythm of 6-hydroxymelatoninsulfate excretion exhibited an advance shift in five subjects, whereas the other three showed a delay shift, and adjustment did not achieve more than one-half of the expected value within 8 days. A significantly different adjustment could be observed in the melatonin-treated group: Seven subjects underwent an advance shift of the expected 9 hr within an average of 8 days. The results suggest that melatonin treatment can accelerate resynchronization of the melatonin excretion rhythm after eastward time zone transitions. The improvement is not, however, sufficiently great that we can recommend melatonin for the alleviation of jet lag.