I'm sorry your flight is because of family illness, it sounds stressful.
1.At LEAST 24 hours before you leave, CALL AA and tell them you are traveling with a lap infant. They will want his name and age.
2.I recommend that you take a copy of birth cert or shot record in case someone asks for it.
3.Weight your bag at home, it hits 50 lbs quick with baby stuff. All baby items are checked for free- stroller, car seat, pack n play, etc. Check EVERYTHING but your stroller and carry on, it can be a long walk.
4. Curbside checkin is best if possible (have some cash for the skycap).
5. Check your boarding pass, it MUST say "WITH INFANT" on your pass, or you will not get through security and must go back to the ticket counter.
6. Make sure your tylenol, benadryl (which I don't recommend to get to sleep, it may backfire and cause fussiness), hand gel, lip gloss, hand lotion, eye drops, etc are all in a single quart size ziplock.
How to take off/land:
What helped for me traveling with my baby was to sit in the window seat and latch him onto the breast nearest the wall while turning my back towards the cabin.I would also put "something" like an airplane pillow in the space between the seat and wall. We had a bit of privacy that way, of course, use your wrap/blankie to cover up and LOWER THE SHADE so that your breast isn't reflected in the glass. I got that last tip from a male flight attendant.
As the plane would start actually picking up speed on the runway I would latch him on. Don't do it as you pull away from the gate, because you may be on the tarmac for a while.
Pack plenty of healthy, easy snacks: granola bar, bags of nuts, etc that are flyable. Or purchase them once you go through security when you purchase the MOST important thing- at LEAST one big bottle of water. You don't know how long you may sit in the plane and you cannot get hungry and thirsty. Bring several anti-bac hand wipes, the gel is not enough. You don't know what you may get into.
Read, music, etc. There is a good chance that the muffin will sleep quite a bit and you can prop up a book on him.
Bring a sweater/jacket, snuggie,etc on the plane (yes, your going to Chicago, but the plane may truly be cold).
several diapers, wipes and 2 quart size ziplock bags for anything stinky. Yay! No bottles!!!! Binky, favorite blanket (or 2), animal, etc. Also several burp rags. Definitely bring extra clothes- I would take a footie sleeper- easy, small, cute if there's a mess. Bring toys that will distract with bight lights/ small squeaks, etc. Don't worry that it will be loud- remember how loud the plane is, you can't hear anyone else's stuff.
Also, at this age, the flight attendant will possible love to carry him around for a bit- that happened with me and was one of my best flights ever!
Changing tables: There is one in the lavatory, right over the toilet. It is tiny and cramped. Not great. Definitely change him right before you board- even if he doesn't feel icky. Wipe those tables down with the earlier mentioned anti-bac wipes!
I'm not a germ freak, but airports are truly nasty. I see people lay down the softy blanky and lay the baby on it, then use the same blanky to wrap up the baby after it has been on the floor with 1000's of shoes. ick. I used to carry a thin cotton receiving blanket rolled up tight that I could always lay down (wrong side down) on the floor if I had to. Of course, once they crawl, it's all over anyway.