I can fall asleep almost anywhere. I routinely fall asleep in the break room at work. Once, I was helping a friend fix his car, and I fell asleep on his garage floor when he went inside to get water.
But in a hot metal tube tearing through the sky, with my neck all kinked? Get out of here, man.
Noise cancelling headphones and the antihistamine tablets that say “will cause drowsiness do not operate machinery or drive” washed down with a pint of beer. Sleep for 6 hours no problems.