Oh my! Sixteen hours...my poor Julie can barely take 16 minutes in her carrier going to the vet. She is not one to hide in boxes or bags and putting her in a carrier really hacks her off. She was rescued as a stray at a very young age...I don't know if she had a bad experience in a small space or what, but she sure doesn't like to be contained. I would have no choice but to sedate her on a long flight.