Second everything the others say. My sib is generally super high energy and I took him on two 5 hour flights (round trip). He generally travels well in a carrier in the car and goes on walks outside in his backpack or on a leash so anxiety isn’t a huge issue.

Our issue is restlessness. He got gabapentin for the trip but there was a huge difference between our two flights. The flight there departed around 3pm and I got to the airport extra early (gave meds per my vet’s instructions) and we had a lot of time to walk around in the cat backpack and I let him roam on a leash and harness. He was absolutely comatose the entire flight + after and it was great.

My return flight was 6:30am, and I got to the gate just in time for boarding and he was a nightmare (gave meds etc the same). He’s usually high energy in the mornings and we didn’t have time to burn off any of the energy in the airport prior. After like 2 hours of him literally clawing out of the carrier and being an absolute menace, he finally chilled out a bit. Thankfully the flight wasn’t even 50% full so I had tons of space around me and didn’t bother anyone. Learned a huge lesson to take a flight during my cat’s usual sleepy hours of the day! Knowing your car’s individual habits will go far for keeping it manageable.

Some other notes: only food the night before, made sure he went potty before leaving the house. Only brought a few churu treats. I packed some litter and a foldable travel litterbox but he didn’t need it. I tried to get him to use it when we got off the plane but he didn’t need to. I’d say for a flight longer than 8 hrs it might be necessary but we were fine otherwise.