I'm someone who takes prescription meds to get through a long haul flight. I hate flying and tend to be a ball of nerves every time I do. If you're that way inclined, go see your doc at least 2 months before your flight tell them you're an anxious flier and they help.

I say 2 months in advance because one time I went to the doc 2 days out and asked for something that would put me out on my 12 hour flight to the US. She prescribed something that did absolutely nothing, but when my partner took it, he was laid out. Drugs are different for everyone.

When I flew to London last year, I went to my doc and we tried a few different drugs to see what worked for me, lorazepam and diazepam didn't work. I felt nothing with them where others would. It ended up being a mix of Xanax and quetiapine that did the trick and I was conked out for about 9 hours of a 12 hour flight. Which was great, was asleep before the plane took off and woke up with enough time to watch a movie and have something to eat before we landed.

If at all possible, make a stop over of even a day. Doing the entire 24 odd hour flight with 2 hour layover in between in an airport is brutal and not recommended.