Sleepiness on the flight deck: Reported rates of occurrence and predicted fatigue risk exposure associated with UK airline pilot work schedules

Survey and field studies conducted with commercial airline pilots suggest that in-flight sleepiness and related involuntary sleep phenomena are experienced by pilots during their duties. However, for methodological, practical and commercial reasons, there is a lack of publicly available research data of per-flight hour rates of sleepiness experienced by pilots or predicted fatigue risk rates associated with pilots' hours of work. This empirical field study sought to address this gap by collecting self-reported sleepiness/alertness ratings from pilots from 18 different UK airlines via a mobile phone app over the period of August 2017. In tandem, predicted sleepiness levels and sleep opportunities associated with participants' flown rosters were investigated using biomathematical fatigue modelling. Findings indicated that a quarter of all flying duty periods were predicted to be preceded by a main sleep opportunity shorter than six hours, whilst 10% of all flying hours were associated with elevated fatigue risk levels. Pilots reported 7.3 reports of involuntary sleep on the flight deck per 1000 flying hours, which represents a rate far greater than that previously reported to the regulator. By comparison, the rates of predicted and recorded fatigue-related incapacitations greatly exceeded the target rate of medical incapacitation permissible under the medical incapacitation safety standard for commercial aviation of less than one occurrence per 1,000,000 h.