Originally Posted by ERflyer

Some would say it is worse than being inebriated. Everyone should read “Why We Sleep” by Matthew Walker.

“... studies in the US have shown that when you limit [medical] residents to no more than a sixteen-hour shift, with at least an eight-hour rest opportunity before the next shift, the number of serious medical errors made—defined as causing or having the potential to cause harm to a patient—drops by over 20 percent.”

Additionally, some of the worse accidents and incidents in history had lack of sleep as major contributing factors:

Exxon Valdez:
“Early reports suggested that the captain was inebriated while navigating the vessel. Later, however, it was revealed that the sober captain had turned over command to his third mate on deck, who had only slept six out of the previous forty-eight hours,”

Chernobyl:
“ ... was the fault of sleep-deprived operators working an exhaustive shift, occurring, without coincidence, at one a.m.” [Yes, there were other factors - as always.]

Luckily not in the book:
A certain airline:
One pilot became ill immediately after takeoff. This resulted in the other two pilots not getting a rest break as they should have and not sleeping during the 9 hour all night flight. The end result was landing a wide body aircraft on a taxiway early in the morning. Fortunately there were no other aircraft on the normally busy taxiway.