We travel with two chis each of us has one in its carry on. We're lucky they go right to sleep and remain quiet the whole trip. The one time I had an inadvertant layover I was traveling with one only , gave him some water and he went back to sleep. They can do w/o going potty all nite so a few hours doesn't matter to them when flying. The general rule that I'm aware of is only two per plane as far as I know. I think the ticket price is outrageous when you see what people bring on board as carry on.
