According to all applicable aviation laws and regulations, a pilot must be sober, healthy and well-rested upon commencement of his duties on board an aircraft. Actually there does not exist any precise definition for a pilot’s state of mind. It does not really matter whether he is sad or cheerful - the only thing that matters is that he ought to be adequate.
At times, pilots fell asleep during the flight. As it turned out later, one of the causes was a crew error, i.e. they had forgotten to check the pressure setting before the takeoff.
It is common knowledge that the higher is the altitude the more rarefied the air is, and there is insufficient oxygen for breathing. Unfortunately, when the oxygen content gets extremely low it inevitably leads to loss of consciousness.
Naturally, an airplane is equipped with oxygen masks but for some technical reasons the crew and passengers failed to use them. That’s exactly what happened to the Helios Airways aircraft 25 miles from Athens in 2005.
It must be noted that cases when the crew falls asleep are considered to be quite rare exceptions but it is they that led to dangerous situations and disasters.
More than once, pilots just fell asleep during a level flight when autopilot was performing their job. Air traffic control service concerned by the absence of pilots’ voice conversation had to engage military jet fighters to accompany those “mute” planes, and flight attendants rushed to wake the crew.
If you notice or feel anything unusual during the flight do not hesitate to immediately communicate this to a flight attendant.
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