Retired airline captain Denny Kelly says the pitch black overhead bin is dangerous for any live animal.
"There is no circulation at all in there," Kelly said. "They're scared, their heart rate goes up and they use more oxygen. And there's not enough oxygen in the first place, that just makes it worse."
Kokito's owners hope others learn from this death. The family says the flight attendant claimed afterward that she didn't know there was a dog inside the bag. She's been described as distraught.
The American Kennel Club says a French bulldog's short face can make its breathing less efficient. They stress easily, increasing their need to breathe.