I have 2.5 y.o. twins and have flown 16hrs+ with them several times, including at about 11mos. If you haven't introduced your DD to sippy cups with straws yet, I highly recommend you bring one along and teach her how to use it during the flight. It's fun and novel and takes up a bit of time. I recommend the one made by Platex with the soft, rubbery straw thats comfortable to chew on. The basic model comes with a blue body and yellow top. Bring a couple of baloons. When she melts down, inflate one and let her play with the tied part...show her how it snaps back and maked a noise.
If you haven't introduced Cheerios yet, now is the time. Don't worry about food too much, it's normal for a small child to just drink milk/juice/water on the flight. If you are really concerned, find a jarred food she will eat at room temperature and bring one on the flight.
I'd recommend bring a change of clothing for you and the bub incase she throws up or spills something on herself or you. I include undergarments for myself as I've been vomitted on and had drinks spilled in my lap.
Don't worry about too many toys. She'll likely find the magazines interesting to pull in and out of the pocket, and the plastic drink cups are fascinating. Just make sure to get rid of them as soon as the crack cuz then they'll have sharp edges.
When you check-in, ask if the flight is full. If it's not, ask for an empty seat next to you or even your own row. Most of the time, if it's available, they'll give it to you. If you bring a carseat aboard, it'll have to be forward facing. Unless you're child is really happy sitting in a carseat, I'd recommend not bringing it aboard as it make maneuvering in the row very difficult. In anycase, I find it easiest and most comfortable to let the child sleep on the plane seat. The car seat is likely to throw out your back. You'll hold the child on your lap for take off and landing.
Most sources I've consulted do not recommend Evian as it has too many minerals. They do recommend Volvic because of the lower mineral content. If she's already on filtered water, just use the drinking water on board. If it's mineral water, even if it's not Volvic, it' not going to do any harm for a day.
Bring one small board book and teach her how to turn the pages. Buy a telephone toy...if she doesn't have one already, that'll keep her for an hour! For melt downs, I also bring plain spaghetti...no sauce. Keep it full length. They love to play with it and eat it.
I used to also put a bib/smock/apron type of thing on them as soon as we got on the plane. They alway spill things on themselves so this keeps their clothes protected for the flight. I also bring a packet of handwipes and a washcloth. I keep the washcloth wet for wiping their mouths. Bring a non-allergenic lotion as your hands will get dry as will hers from the wiping. It's also nice to use as a massage lotion. One of my DS love getting a hand, foot and face massage on the plane.
Those are my secrets...oh, and don't drink any alcohol no matter how tempting. It will make the adjustment much more difficult.