The flight out was boring. That's a good thing. You never want flying to be an adventure, especially when you know there are two unhappy cats elsewhere on the plane.
Alaska Airlines gets points for making the whole experience as painless for the human escort as possible. They label each animal carrier with a tag that says, "Relax, we're on board, too." The ground crew pulls the tags when they load the carriers, and delivers them to the flight attendants. Then at the other end, they hand carry carriers back to the owners.
We were pretty sure the boys were okay when we heard them meowing outside the odd-sized luggage door. We figured if we could hear them through a closed metal door, over all the noise of baggage claim, there couldn't be anything too seriously wrong.