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.
Ambien, alcohol, etc
Alcohol makes me need to pee often so that can backfire. Makes you dehydrated too. 😅
Exhaustion too. Often travel routines are ridiculous, like having to get up after 3 hours of sleep.