Sleep and biorhythm among intercontinental pilots: the effect of exempting flight crews from mandatory layover and flight times during COVID-19.

Pilots are crucial to the safety of the airline industry; as a result, their sleep and biorhythm, which are closely related to fatigue, play an important role. During the COVID-19 pandemic, the Civil Aviation Administration of China exempted flight crews from mandatory layovers and imposed limitations on duty period and flight times. Given that the effect of this policy on their sleep and biorhythm is poorly understood, this study explores the key factors affecting the sleep and biorhythm of pilots on intercontinental flights and compares the rest status on and after flying days on exempt and non-exempt flights. Eighty pilots flying from China to five countries wore a body movement recorder, which has been validated for estimating total sleep time, sleep efficiency, and interdaily stability. The results of the K-means clustering analysis showed differences in sleep and biorhythm on flying days between departures during the day and at night, west-east and north-south flights, and exempt and non-exempt flights. ANOVA was performed based on the categorization in which each indicator contributed significantly to the clustering (p = 0.000). This study contributes to the literature by validating a new intercontinental flight operation model under the COVID-19 pandemic conditions and proposes critical points for the future management of pilot fatigue on long-haul flights.