How do you sleep on planes

I've never been able to sleep on planes or in vehicles, since i was a kid. maybe its just the sleeping upright part or its just because i cant shut my brain off. Anyways ill be headed to Scotland in a few weeks and we are leaving at 7pm and getting there at 10 am. i really don't want to be awake all day and night. do you fellow ADHD'ers have any tips to fall asleep on the plane ?