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.
I fall asleep long before we ever take off usually by putting a podcast on the earbuds, wrapping a sweater stiff around my neck and focusing on the vibrations from the engine. Usually wake up around landing announcements. Never realized this was a blessing.