
I do all the planning for our trips because I am a travel agent, that's just what I do! I chose Southwest for our flights for multiple reasons. I had heard they are very family friendly, they allow two bags per passenger before fees kick in, the open seating concept works great for families, and they had a good selection of flights for our destination.
On the way to Dallas (Love Field) we had a layover in Houston (Hobby). Why did I put those two words in parenthesis? Because Southwest uses smaller, alternate, airports in those two cities. I wanted people to understand that we did not fly in to IAH- Geogre Bush International or DFW- Dallas-Fort Worth. Was this a problem? No, in fact it was a lot nicer because it wasn't over crowded, security lines were a breeze, and we did not have to race across terminals to get on the connecting flight.
We had an hour delay on our flight out of Fort Lauderdale because they are currently operating on one runway during construction, so we sat in a long line for takeoff. We still managed to get to Houston with an hour between connections.
Gate Check vs. Curb Check for baby items.
Before the trip I purchased "Gate Check" bags for our stroller and potentially the car seat. They can be purchased at any major baby store like Buy Buy Baby or Babies R Us. They came in handy to identify our belongings, but also protect the items. The bags came back with black marks and a few pulls, glad it happened to the bags and not the stroller or car seat. :)
*Please note that the American Academy of Pediatrics and the IIHS both recommend that all infants and young children travel in a car seat on an airplane and that you should never check a car seat because it could be mishandled and damaged.
Lap Infant vs Purchasing a Seat
We elected to have our son ride as a lap infant. When I called for the child's fare, it was nearly $200 more than the adult fare for our trip. We made the decision based on finances and reasonable risk. We felt that in the event of a plane crash, most people do not survive anyway. I know that is a very blunt thing to say, but that's what it came down to for us. The beauty of Southwest is that they have open seating, there are no assigned seats. We figured that if any of the flights were not full we would be able to carry the car seat on, instead of gate checking it, and strap him in next to us.
Our first flight was only about 1/2 full, so we were able to bring the car seat on the plane. It was a tight fit. We have a Peg Perego Primo Viaggio infant carrier. In order to install it I did have to shove the seat in front of his forward a bit. I had to use a seat belt extender to properly strap the seat in for my son. It took a lot of finagling. I actually worked up a sweat by the time the seat was properly installed. If you plan to purchase a seat for your child's car seat or cross your fingers that your flight is not full, please remember that a car seat must be installed next to the window. Simple reason: if you install it in the middle or aisle seat, no one from your row is getting out!
Our connecting flight, from Houston to Dallas was overbooked and so we had to gate check the car seat. I kept an eye on it and not once did they mishandle it.
On our flight(s) back to Florida we had to gate check the car seat as well, but again they were kind as can be to our belongings.
Please review American Academy of Pediatrics statement on lap infants here.

We had no trouble bringing ample formula for our son. Parents traveling with young children are allowed an exemption to the 3oz rule when it comes to milk, formula, or other vital liquids for babies.
If you are breastfeeding, you have it easy. You are a portable bottle!
If you are bringing breast milk or formula in bottles, just declare it when you go through the security line, they will do a simple test on it to ensure it isn't explosive. Most airports have a designated family and disabled line to make it easier to get all your belongings through. The TSA recommends that you only bring enough for the trip. I, on the other hand, know all to well about delays with the airlines these days, please evaluate how much your child may need and bring extra. The last thing you want is to be stuck in an airport with no access to formula or pumped milk.
My son has acid reflux and a nice list of allergies, so he is on a very expensive hypoallergenic formula called Alimentum. He has to take the liquid form because there is corn in the powder version. With that being said we wanted to find something convenient and manageable for our trip. I generally buy large 32 oz jugs of his formula when at home, but once it is opened it must be refrigerated. That doesn't exactly work on airplanes! I purchased the small 2oz nursers that hospitals give and can be purchased in many stores or online. This was convenient. As they are individually sealed and do not need refrigeration! My son drinks about 4 oz at a time, so during the one flight segment that he was awake we simply fed him two of these small bottles (see photo above). I highly recommend this method if you happen to fall in to the same predicament as us.
You can bring cooler packs through security as well. We felt that it would be one more bag, extra weight, and unnecessary worry for us during our trip. The small bottles with the screw on nipples worked best in our case.
If your child takes powder formula, I would recommend the Munchkin formula dispenser. You can pre-measure the powder amount and store it in this nifty container with 3 sections. You can find them on Amazon for about $3 as an add on item! Then just purchase some bottled water once you're through the gate and you're set!