Ok, first, take a deep breath. I just flew with my 9 month old and for me, the anxiety of the flight was worse than the flight itself. The only thing you can do is prepare as best you can, then cross your fingers or pray - whichever floats your boat. That being said, here are some things I've learned over the years with flying with kids (older kids are 11,9 and 8 and all have flown many times)
I whole heartedly agree with the extras. I always bring extra clothes for myself, too. One good spit-up or explosive diarrhea and you're wearing it for hours.
For me, it was hard to give my daughter something to drink while take-off and landing because she had just had a bottle before boarding. I had a licorice stick in my carry-on that I ended up letting her gnaw on so that she was swallowing (releasing pressure in her ears). I would suggest taking something like that, but finding something healthier that she could chew on. I don't normally let my 9 month old eat licorice! LOL!
The other thing I do on flights is to get some of those plastic chain links and attach toys to those. I learned early on that it's no fun becoming a contortionaist trying to retrieve toys from the floor of an airplane - not to mention the germs!! This way you can at least hang on to one end or find something to attach them to. For toys that don't have a place to attach the links, I took heavy duty packing tape and made a "loop" on the toy so I could attach the link.
Speaking of germs, have Clorox wipes and wipe down the area around you. I was pretty nervous about all the touching going on when my baby was exploring. The last thing you want is to get to where you're going and have to deal with a cold on top of it all.
Yes, buy new toys. New things she hasn't seen that will be new to her. I used to try to shy away from anything that would make any kind of noise. However, would the people around you rather hear a soft lullaby from a toy or a screaming child? You can give them that choice if there are complaints. Besides, that's what earphones are for. They are, what, $5?
When my kids were toddlers, I would wrap their new toys-like a birthday or Christmas! For a 9 month old, she may enjoy "getting" to the toy. Of course, the paper may go straight to her mouth, but it may burn up some time while she is unwrapping.
Plenty of snacks and drinks. I've always had great experiences with the flight attentdants. They are usually accomadating and will get you water, juice, etc. if you need it for the baby. I would try to get as much with you as possible. I know this is difficult with the liquids rule, so this is why the attendants are usually willing to help out with that.
I also would absolutely try to get the bulkhead. If it's a 10 hr. flight, I'm going to assume the plane is larger than the domestic planes. If so, I'd still try to plead your case before/when checking in.
I took bubble gum for my older kids and ended up entertaining my 9 month old for a long time, blowing bubbles and popping them just before she touched it. *Be prepared for her to be faster than expected, making sure the wipes are accessible! LOL!
Books are great-especially the ones that have texture to them. Touch and feel horses, farm animals, beach, etc.
I would agree that having a seat for your baby would be ideal. However, I realize that may not be possible. In addition to being able to put her down in her seat while she's awake to play with her, you'd also have a place to put her when she's sleeping. I held my daughter through her nap on our return flight. I was grateful she was sleeping, but it was VERY difficult to hold her at an angle that her head wasn't sticking out into the aisle, therefore getting bumped every time someone walked by. Not to mention the beverage cart. Her legs were in the seat next to me, but that was ok, since my 8 yr. old was sitting there. I also had to wrap her blanket around her head, to cover her ears, so that all the loud pilot/attendant announcements didn't wake her. up. But, my daughter is a light sleeper. You may not have that problem.
I'm sure you already thought of this, but having a stroller (small, unbrella type) to get her to the gate is a must.
This is what I've come up with for now. Basically, the bottom line is you will do your best. I really have never had anyone on a flight get upset with our children. My kids fly really well, but most the time, there are parents, granparents and other kids on the flight that are more than happy to entertain kids when your efforts are getting old. I know there are horror stories out there, but like I've said, I've flown a dozen or more times with kids of all ages and remembering to breathe is the first step. If you are anxious and stressed out, your daughter will feed off of that. It is a long flight, but if you take out the 4 or more hours she will be sleeping, it gets easier to think about.
The best of luck to you!!