G.L.
FIRST - You have to relax. You must realize that there WILL be "bumps in the road" ... but you will reach your destination eventually. Stay flexible! If you can stay calm and relaxed, your child will be more likely to stay happy and calm as well. Remember that all of the adults you encounter were children once upon a time and if they appear unhappy or unkind -- it is THEIR PROBLEM, NOT YOURS. You can do your best to help your child be a pleasant traveler - and that is all anyone can expect ! Lots of smiles .. they are contagious!
I have not traveled space-A in years, so I can offer no information on that front. Just be sure to check the rules and regs for food and beverages. You both need to stay hydrated to stay healthy and happy on your journey!!
When we travel with our 4 children, I always bring more than we need ... but I always have what we need, if we need something! With one child, you should be able to get your "stuff" in a large carry-on back-pack. Crayola's mess-free color wonder products are perfect for travel. And you can always pull out a regular notepad and pen or marker in a pinch. If your daughter has absolute favorite things (and you can risk losing or getting them dirty) .. bring one or two small things to keep her comfy (thoughts of home). I usually have at least one new, exciting thing to pull out of my bag to grab interest. Quiet toys with lights are usually attention-grabbing. When you are in the US, look at Target for a an orb with spinning lights inside,$5 - Gadget brand, I think --- we have been through several of these, and I will keep buying them!!! You can at least have it for the return trip!
Bring ziplocs to stash leftover airplane food in so that you can consolidate your meal tray mess and get up and out of the seat fast if you need to - without wasting what you might need later. Sometimes the flight attendants have you wedged in for a miserable amount of time. You can also use the ziplocs for diapers.
I usually carry an empty sippy cup for filling up on the plane. Don't be afraid to ask for more drinks! Thirsty children are grumpy children!!
I have learned to change my children's diapers on my lap or while they are standing. It saves me from having to wait in line and keeps my children away from some of the germ-laden changing areas. I try to be discreet and mindful of others ... but clean bottoms make for happy children as well! Practice a lot at home before trying out and about. The font seat of your car is a good, cramped area that compares to a plane seat.
Safe and happy journey!