I'm not up on the rules but why would they offer the option of bringing pet crates into the passenger area? Maybe for tropical pets that require a warmer environment than below? Or maybe just to sell another half ticket? The story said "the bag was partly obstructing the aisle". So was the bin in a bag? Or did the passenger pay to bring a bin that fit under the seat but they brought the wrong bin? IDK the circumstances, but anywhere you bring a pet, you have a certain amount of responsibility for the animals wellbeing, regardless of what you are told. If the owner had bothered to open the overhead periodically to check on the puppy and reassure it, the puppy would have been fine. The overhead bins, while not suitable pet habitats, are fully withing the control of the passenger who puts stuff there. If I left my puppy in a closed box right within reach for six hours and it died, I'm not sure how righteous I'd feel about blaming somebody else. Not that the attendant wasn't also at fault, but fault is everywhere, and we need to protect our loved ones from it all the time.