I've flown now twice with my son, once when age 12 months, one at 24 months. It was just a 3 hour flight though. Yours is longer.
At 12 months, he DID sleep, as I planned our flight time around his naptime. I nursed him on the way up into the air and he slept in my arms almost the whole trip. WHen he was awake, I had toys, books, snacks, and a mini DVD player with me to keep him occupied. He was not yet walking, so he didn't have a desire to get down and walk. So I would HIGHLY recommend a DVD player with some familiar and also some new Baby Mozart DVDs. I brought his most interactive books that we had (flaps and slides and such).
I was on my own, so had to hold off going to the restroom the whole time. Not fun. If you're flying solo, I'd recommend you get a two-way flight so you can get out and entertain baby and relieve yourself too. I don't know what red-eye flights are. But if you take a one-way trip, then remember that there are no diaper changing tables on the flight. I suggest you get diapers a size bigger than normal so they don't leak if you can't change baby real quick. Bring EXTRA diapers, as sometimes flights make baby's tummy upset and they have blowouts. That being said, bring an extra outfit for baby AND an extra shirt for you just in case.