<font face="Verdana, Arial, Helvetica, sans-serif" size="2"> wingnut said
...take an eye mask, ear plugs (or noise cancelling headphones), wash bag and, most importantly, rescue some "do not wake for meals" stickers from a previous flight.</font>
Good start - I suggest you have multiple pairs of earplugs to start, at least one spare eyeshade, and absolutely do not forget the toothbrush and toothpaste easily accessible. Also some kind of moisturizer; I use L'Occitaine because I have lots leftover from DL BE, but you want something like that - waxy, not too smelly...
Oh, and yes - slippers. You want something light but with a moisture proof or resistant sole (lavs are always Iffy, never mind 9 hr flights).
And for coach, extra bottles of water. I know non-US airlines are better about water service in coach than US ones, but you haven't said what airline you're flying, and you can't have too much water available.
Also, I Never leave home without my footrest (if I knew where my aunt bought it, I'd tell you - there's something similar, somewhat fancier at magellen.com). Yeah, I've used a carryon bag as a footrest too. No more.
Check your airline. Drinks are not necessarily free int'l in coach. If that matters, Athena53 has the right spirit, ahhem... By all means enjoy, I do (but drink water too!)
Take a good travel pillow, but an inflatable one - another no-brainer. The one I have now is from Eagle Creek (I think) - it inflates easily, and adjusts the air pressure by a button - works well - and has a nice fuzzy cover with a little pocket which holds my earplugs and my eyeshade, so I'm ready to play Pinball. It does take up more room in my "personal bag" than the old Samsonite inflatable pillow did, but it's really comfy , and actually works the right way around.
Blankets are up to you. I survive with whatever I find. The bulk they take up is significant - don't bother, unless you're taking a fashion statement wrap on plane with you, in which case that's your thing.
Food: you already know it's very good odds that what you bring on will be as good as or better than what you'll get served in coach, and probably than what the other cabin get too. So go for it!
Drugs: I Won't Say No... I sure as whatnot wouldn't plan a long flight (maybe not 9 hrs, but 10 or more) without some Ambien at least in theory. I don't even sleep with it, but I get decent rest. It makes the difference between having an OK day at my destination and being a sleep-deprived zombi.
[This message has been edited by GG (edited Jan 16, 2004).]