I did exactly the opposite last year 
I bought some over the counter sleeping tablets, my mp3 player and my two favourite books.
Basically I was so excited I hadn’t slept the night before so I would have slept 8 hours out of the 15 travel time which was good. I read a lot and wrote in my diary and just generally chilled. I was so exhausted from the anticipation (i counted down that trip from 150 sleeps out 
) that the plane ride was actually quite pleasant.
My last flight to the UK went Christchurch-Auckland-Los Angles-London in one go… something like 28 hours of continuous travel. :eek:
I’d done the flight before with the aid of a walkman, and a stack of books, but this time the flight from Auckland to LA just seemed to be taking forever- I’d sleep for what felt like ages, wake up, and realised I’d only dozed off for an hour or so.
After the plane took off from LA, I took advantage of the in-flight bar service and had several stiff drinks with (and just after) dinner, along with a couple of glasses of water to stave off dehydration. I woke up when the wheels hit the tarmac at London Heathrow, and felt really good- rested, relaxed, and ready to fight my way through the labyrinth of the London Underground and the British Rail Commuter network to get to the place I was staying.
This last trip to the US I stocked up on books, only to discover that the airline had installed LCD screens in the headrests of all seats in the plane, with an amazing selection of movies, music, TV shows, and other stuff to keep oneself entertained. I watched a heap of movies that I’d been meaning to see but would otherwise never gotten around to renting (Stranger Than Fiction and The Last King of Scotland were two movies I’m extraordinarily glad I saw), and I spent the flight from Australia to the US watching movies and reading. On the way back, I was so tired from all the running around we’d been doing that I basically fell asleep after they served dinner, slept for a good 8 hours, woke up in time for breakfast, and watched Malcolm In The Middle until they switched the system off for landing.
In short, my secret is a couple of stiff drinks with a couple of glasses of water, a book, and in-flight movies (where available).
I didn’t mean to sound like I’m advocating consuming alcohol like a football hooligan. I heartily agree that lots of water should be consumed. However, I find that a cocktail before, and a glass or two of wine with dinner, can greatly relax me and actually help me sleep.
My last long distance flight was 13 hours New York to Dubai in November and it worked great for me.
Heathrow - Auckland and reverse a couple of times via Asia (28 -30 travelling hours)
Books, inflight entertainment, eat, sleep
Always set your watch to destination time as soon as you board the plane. Try to shift your sleep pattern to match the destination in increments.
Once you arrive, stay awake while it is light, and don’t go to sleep till it is dark.
Si