The drone of airplane jet engines is like church for me - straight to sleep for me in both cases! And, I don't even have to be tired for it work on me.
Longest I've been on a plane is back-to-back 8-10hr legs from US to India. When changing planes in Paris, my colleague and i enjoyed good conversation, but later I found out that he dind't remember a bit ... due to Ambien. It hits everyone differently! I don't need it; all I need is the drone of jet engines.