I think the single most important thing you can have is a sling. Don't take a pram if you don't need it at the other end; if you do need it, then it's easier to check it asap (although you can keep it all the way to the gate).
For luggage - wheeled trolley-style luggage is essential, and only one manageable case, if at all possible.
At the airport, you are advised to take as little cabin baggage as possible, and any liquids (except formula milk essential for the flight) has to go in a single, small ziplok bag (you can buy anything you need on the other side of security). Take a change of clothes and reasonable number of nappies/wipes for the baby, a couple of muslins, and a fresh top for yourself.
If by any chance you were thinking of giving up breastfeeding before the flight - don't! It makes it so much easier to be able to comfort your child on the flight and also not to worry about taking milk with you.
If you are on a long flight, you may wish to ask for a bulk-head seat, where you can get a bassinet for the baby that screws into the cabin wall. If nothing else, it's a good place to put all your junk
As with anyone, you want to dress with security in mind. You'll probably have to take your shoes off, so slip ons are a good idea. You probably won't have an underwired bra, but if you do, it might be an idea to switch for a sports bra or something soft. If you wear a belt, you may have to remove this, so you might want to wear sweats/fitness pants instead.
If you are travelling alone with the baby, you may need to ask for help from staff or other passengers from time to time (eg to hold the baby when you can't). Don't feel you need to do it alone.