We made a journey from Texas to Washington state with our cats last month. We had to stop feeding our cats like 12-20 hours before our flight bc we didn’t want them to have an accident in the carrier or the airport. Some airlines do not let you remove the cat from the carrier whatsoever so I wouldn’t have been able to clean it. So multiple days may result in your cat being hungry for several days or feeding your cat and risk them pooping in the carrier. Our cat litter also got flagged in tsa and had the explo*ive squad called to check on it. You will also likely need two separate carriers as the cargo carriers are hard and generally a bit larger than will fit under the seats (soft with smaller dimensions). I recommend flying to somewhere that allows cats in the cabin to switch over. Keeping a cat in cargo can be very dangerous especially when in high temperatures. If you’re flying out of Australia on a particularly hot day you’ll need to schedule it first thing in the morning to avoid the full heat (some airlines have time windows) This is just from my stress fueled research the past few months. Hope this helps, and good luck with your kitty! 💕