In-flight sleep as a pilot fatigue mitigation on long range and ultra-long range flights : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Sleep/Wake Research Centre, Wellington, New Zealand
Objectives: Long range flights operate around the clock with long duty periods for pilots. To
mitigate the effects of fatigue, these flights are operated by augmented crews, providing
each pilot with the opportunity for sleep in on-board rest facilities. This thesis used a mixed
methods approach to investigate the use of in-flight sleep and the factors that influence it.
Methods: Retrospective survey data (291 pilots, five studies) were analysed to provide an
overview of pilots’ sleep at home and investigate potential relationships with in-flight sleep.
A second project monitored the sleep, fatigue and performance of 35 pilots operating a B767
flight route between Atlanta and Lagos. These projects were supplemented by thematic
analysis of pilots’ logbook comments on in-flight sleep (N=123) and on the way they manage
their fatigue (N=629).
Results: Pilots viewed in-flight sleep as an important fatigue management strategy and
actigraphic sleep monitoring confirmed that the B767 pilots made good use of their in-flight
breaks for obtaining sleep. Self-ratings of in-flight sleep quality reflected ratings at home,
but were usually poorer. Pilots indicated that the type, location and design of rest facilities
affected sleep quality and duration, and identified strategies for minimizing sleep
disturbances and improving alertness. Comments indicated that prior knowledge of inflight
break allocations can influence the planning of pre-trip sleep, use of naps, and in-flight
sleep. Actigraphic measures of sleep indicated that the B767 pilots obtained more sleep in
the 24 hours prior to departure than during baseline days regardless of their subsequent
pattern of in-flight breaks, but it is unclear when they were advised about their break
pattern. Ratings of sleepiness and fatigue increased across the B767 flights, but
psychomotor vigilance task performance at the start of duty and at top of descent was not
associated with prior wakefulness, prior sleep duration or in-flight sleep duration.
Conclusions: In-flight sleep is a well-utilized and effective fatigue mitigation strategy that
may be supplemented by other strategies such as flight preparation techniques. To further
reduce pilot fatigue risk on long range flights, additional research is warranted into the
effects of flight preparation techniques and in-flight break patterns.