I have flown several times with my bunny, and all of them ended up being at least 12 hours of travel time, so you should be totally fine with a 5 or 6 hour travel time. In my experience, the actually flying part, in the plane, was the least of the challenges. You’ll want to start thinking about how you plan to get through security with your bunny. Is your bunny nice and calm when being held, or is he likely to try to make a run for it? The security checkpoints are crowded and noisy with a lot happening. You’ll have to take bunny out of the carrier and have the carrier scanned while you go through a metal detector with bunny and then have your hands swabbed. Then, they’ll finally let you put bunny back in the carrier. My bun is great with all of this and calmly sits in my arms through the whole process. However, if you think you may not be able to securely hold your bunny without fear of him taking off in a strange environment with a lot of commotion, you might want to think about requesting to have your belongings checked in a quiet room, which you can ask for. Also think about bringing along some extra greens. My bunny refused to drink any water, but would eat greens in her carrier while we waited at the gate. Once on the plane, you should be good to go. He’ll probably be nervous, but the space under the seat is nice and dark and he’ll probably settle in for the flight just fine. Mine would squish all the way to the back of her carrier so that she was basically sitting on my feet, but that seemed to help her remember that I was still there with her. I’m not sure when you’re traveling but if it’s going to be hot outside, make sure to put the air from your vent on facing towards your bunny on the floor until take-off. Once in the air the planes usually cool off nicely, but they can sometimes be hot while sitting on the tarmac. Other than that, I wouldn’t worry too much about pressure change. Their ears are designed to pop same as people, so while he may have never experienced this before, he should be fine. Good luck and happy flying!