we traveled with DS when he was 7 months. it wasn't as bad as I prepared myself to be. If you are able to purchase the necessary items when you land, I recommend doing that. trying to pack all the diapers, baby food, wipes, it's a lot and way to much to carry, on top of all the clothes and toys.
We were able to check the carseat and base with our luggage (it was considered as one piece of luggage, flew Southwest, so I had one suitcase and carseat and didn't have to pay extra) then we gate checked the stroller no extra charge either.
I was able to get through security with a couple of jars of baby food and one bottle premade. I didn't need more than that for our trip. Just have to take it out of the bag and they check it, didn't give me any problems.
Brought lots of toys for DS for the plane, luckily it wasn't full, so we sat in the back and got lucky with an empty middle seat; that was nice because he was able to crawl around a bit. He drank bottle when we left and a little when we landed so his ears wouldn't pop, and he did great. He slept for about half of the flight, the other half he was more interested in playing with DH iPad and Laptop. he was also really intrigue with staring out the window. overall it was a good experience! =)
good luck and have fun