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 haven’t been on a very long flight. Longest was 2 hours. Every time I keep my Kindle ready. Have multiple podcasts etc. But right after take-off, I go off like a bulb and wake up only after landing
Something to do with a combination of pressure difference, engine noise and all. Also it’s pretty cold usually