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 used to not be able to sleep on airliners, but then I got a job that required I fly on one once a week. By far the best way to make time pass fast.