I recently took Ranger with my from Idaho to Arizona via Uniter Airlines. It was great. We had no trouble, and he actually seemed to like it (what yorkie doesn't want to be with mommy all day!) I was so surprised that I was never asked for any documentation- I don't think the flight attendants even knew he was on board?? Maybe someone else can answer that?
Anyway, I took a little baggie of his food and throughout the flight gave him a few pieces here and there. My vet advised me to feed him half his breakfast I think it was three hours prior to the flight, so he wouldn't have an empty tummy, but wouldn't be too full, either. He was starving when we got to AZ though!
As none of the flight attendants seemed to notice/care, I put his carrier on my lap and held him throughout the flight. On the way home, it was night-time and I actually kept the bad open on my lap, and he was so tired he just put his little head on my hand and slept the whole way. At the end of our flight, he woke up and the girl that was sitting next to me finally noticed him at that time and told me she thought I had been talking to myself the whole flight!!
Good luck!!