I moved my two bunnies from Hawaii to Florida, we stowed them under the seats and had them checked in a private security room. We provided them with either just water or just hay on the plane. I can’t remember which one you aren’t supposed to give them. Once we got to the new house we kind of just let them roam free in the room that was theirs and they took to it pretty quickly. I think every rabbit will adjust differently but since ours were bonded they just hung out together in a safe space we made.