ABSTRACT
Jet-lag and day-time sleepiness cannot be avoided in transmeridian operations, because work hours of aircrews interfere with the circadian system through irregular work-rest schedules and rapid time-zone transitions. Although the primary cause of accidents is usually the human factor, jet lag and sleepiness have seldom been officially identified as causes of inadequate functioning in the cockpit. However, research clearly indicates that flights at night and/or across time zones will impair performance and reduce safety. Research on countermeasures have focused on on-board napping, crew augmentation, behavioural strategies against jet-lag, light treatment and melatonin administration. Regrettably, scientific knowledge has been successfully transmitted to only a very few national authorities responsible for work hours of aircrews.