I fly back and forth to Florida with my two Shih Tzu's in this carrier. He is 17 pounds and she is 12 pounds. They only need enough room to curl up and sleep, which they do anyway. This fits perfectly under the seat in front of me. I was called out on it at the check in counter, the agent telling me that it was too big. I simply walked over to their baggage display and placed this right in their "carry on" bin, with the dogs in it. If your dog is skittish, let this sit out for a while before you fly. Place it near their bed and put them in it every now and then so they get used to it. 

Pros: Perfect fit.
Cons: None.