1.Circadian rhythm is the internal biological clock that regulates body functions based on our wake/sleep cycle. It can be disrupted by changes in sleep pattern. Pilots and aircrew members may experience circadian rhythm disruption, specifically “jet lag” as they work.Pilots often travel across time zones and work when others would normally be asleep. This can affect their internal biological clock and disrupt normal sleep patterns which canlead to fatigue, difficulty sleeping, changes in mood, injuries, stomach and intestinal symptoms, and other health problems.2.Fatigue is a condition characterized by increased discomfort with lessened capacity for work, reduced efficiency of accomplishment, and is usually accompanied by a feeling of weariness and tiredness. Causes of fatigue can range from boredom to circadian rhythm disruption to heavy physical exertion. Any fatigued person will exhibit the same problems: sleepiness, difficulty concentrating, apathy, feeling of isolation, annoyance, etc. None of these are good things to have happen to a pilot, much less if there is no one
