I used to be a flight attendant. 2007- 2010. These things happened quite frequently. So it's not uncommon. However having your cat out of the carrier during the flight may be objected to by the flight crew for safety reasons, especially during an emergency. So not to get you worked up or anything, but traveling with an ESA (emotional support animal) is very common, but having the animal out of it's carrier is usually frowned upon.