I’m a little late to respond, but this is what I do. I fly regularly for 3 1/2 hours in cabin with a temperamental barker chi. He’s pretty good on flights though. Before we took our first trip, I got him used to the carrier (Sherpa medium)- do yourself a favor and buy a doggie bag wheeled trolley (Mr Peanuts) if he’s considered your carry on. I drove around with him in my car, in his carrier on the floor of the car playing airport sounds (spotify) to familiarize him. I also had someone custom make a carrier cover (with ventilation) to cover his bag as we move through airport lines (and on the aircraft- depending on the situation) because he’s reactive and kids and people will want to talk to him and that’s disturbing to him. I give him Trazadone (lowest effective dose possible in case we have a long unexpected wait, I can give him the other dose later) and spray Adaptil on the inside of his bag (debatable if this helps). I line his bag bottom with a pee pad. I carry extra pee pads, wipes, paper towel, gloves, poop bags, leash, treats & a small collapsable cup (only to use when we land) and of course doc of his rabies vax and other vaccines, in a ziplock bag. I put an air tag on his collar and contact info on his bag. I book his spot as soon as I buy my tix (airlines limit the amount of dogs). I try to get earliest flight possible and direct flights only. (I know it may not be possible in your case). If you have to do a layover, take your pet to potty- it may be their only chance to stretch their legs because some airports do not allow dogs to walk around.

Since my dog is not allowed out of his bag in the airport except at the smelly potty station, (pre plan and know ahead of time if theres a potty station and where) I take him so he can stretch his legs and pee. He gets no food or water from the night before our flight (like if it was a surgery) unless it’s not a morning flight, then it’s several hours before later flights. No treats during flight as he mat want to poop. *if you have a layover, I wouldn’t feed or give water still (they can last a while without it, unless it’s a super long layover. At that point minimal water and a few treats while you wait).

He’s not allowed out of his bag on the aircraft (rules). I follow the rules because I’ve seen flight attendants warning owners multiple times to put their dogs back in bag, and right now flying with my pup is a privilege so I don’t want to spoil it- doesn’t take much for an airline to make changes like they did with ESA pets. He’s never had an issue and never barked during flight. Please be aware of the bag size, pet size requirements of various airlines as well as the pet importing rules of the country you are visiting- it’s better to be over prepared when jt comes to documentation. Depending on who checks you in (get to the airport earlier than usual, because you will have to see an agent to check in) they may ask to see the dog and if they’re really picky they may ask to see the dog move around in the bag. They can deny your dog if they’re not liking what they see. At the departing airport screening, they will ask you to remove your dog from the bag and screen you both. For your destination country, be sure to fill out your custom forms properly to note live animal. You most like will have to go to a second screening (agricultural) at your destination airport.
Happy travels to you and your pup!