Bathroom issues with cat on 9hr flight?

Yes use the dog carrier your cat could get sick holding it in so long also cats get pretty stressed during long travel so you have to make it as comfortable as possible try and make sure the carrier is big enough for some of his toys you may want to bring him on board with you if possible and sneak him into the bathroom so you can change the pad calm him and give him treats when necessary if he needs to be under make sure hes comfortable and has plenty of food and water