I, too, have traveled with small children many times. Cross country, flights even. Just remind yourself that all you can do is your very best. I have found that even when my children have been difficult (crying, fidgety, etc) most people around us were okay because they saw that I was actually trying to do something about it. Not yelling or being overly cranky with them, but pulling out my bag of tricks and trying my hardest to stem the tide. Nothing is harder to take than crazy kids with parents who don't see it, you know?
Come prepared (snacks, if she uses a bink I would bring that - and a few extras!, little games or gadgets that might keep her content.) When my kids were squirrely, I also found that if I simply just walked up and down the aisle with them, most people were friendly. I figure they'd much rather have a toddler walking around smiling at them than trying to stay put and screaming bloody murder. I always had sippicups with straws for them to suck on the way up and down (helps with the ears.) And even though it sounds young, I started allowing my 17 month old daugher to suck on ring pops to keep her mouth occupied, and hence, quiet. There is no stick in a ring pop, so nothing to bite off, it's all plastic, and it lasts forever. If you decide you want to bring a few just as a backup, I highly suggest getting only the red ones - you can't imagine the mess the blue and purple ones make!
Bring lots of wipes - but again, I would rather deal with a messy quiet kid than an unruly clean one.
No matter what you do, there WILL be people who run in terror when they see your beautiful child. Ignore them - they clearly don't have kids. And accept help if you need it - you never know when a kindly looking grandmother might offer assistance. Good luck to you! You can do it!
Anyway, PP had some good ideas. Thanks! 
