We flew to Indiana about a year ago. Pinky did great and it cost about $80 extra. She had to stay in her carrier and we also had a connecting flight. I had the doggy panties on her just in case and a couple of treats I would give her during the flight. She was very quiet and good. I practiced with her in the carrier for about a month. She got to the point where she would jump into the carrier to go and just loved it. Here is a picture of her on the airplane with her little nose sticking out.
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The guy behind us said he was surprised we had a dog, she was so quiet and good.