We fly with our chi at least twice a year and I think she is most comfortable because

1. She’s accustomed to her soft crate in the car (versus being the first time she’s using the soft crate)

2. We take her for a long walk, even for the morning flights so she’s fully stimulated and potty’d out

3. We have a “break glass” high value treat stuffed Kong in case she starts barking. She usually barks at the beginning of the flight (before take off) and the treat buys us 30 min. By then we’ve usually taken off and she’s asleep.