My current puppy flew in via United. His breeder uses them all the time. She breeds Czech German Shepherds and always has a waiting list for working line puppies, so she’s a frequent puppy flier. She’s used United for many years without any issues.
My pup was just fine.
I am always nervous about flying in a dog, though. Especially when there’s a stop over, which there usually is. The most anxiety provoking was a lovely GSD girl I brought over from Amsterdam to LAX. I think the shipper used Delta Dash that time. She also was fine and happy.
A lot of it has to do with the fact that I only buy GSDs with excellent, rock solid nerves. Thus, they don’t show a lot of signs of stress.
When my daughter and son-in-law were moving to CA. ,last summer, Jet Blue refused to fly their Golden due to the July heat. They opted to drive for 5 days and the happiest one on the trip was the dog. Her favorite place is in the car so she was in heaven. It actually turned out to be a great trip, their youngest drove with them while her brothers flew.