Hey Baddog,
There is some good advice on this thread, but here are three more things:
1. We do well when we get a pet confirmation for the flight as well. Even flights that allow pets can sometime refuse the pet for too many pets in the cabin. If your pet has the confirmation, your pet will be accepted.
2. You must have a health certificate dated within 14 days of travel, which usually means close to departure if it's round trip.
And lastly,
3. Check the size requirement of the crate for the actual plane booked, as every plane has it's own restrictions. The reservation team can help you if you ask direct questions.
This information is compliments of Mary who travels with her dog all the time
