Flying with cocker spaniel?

How to travel (by plane) with pet cocker spaniel?

We are looking to fly to Florida in a couple of months, and we have a cocker spaniel who is about 30 lbs, and he’s a very long dog.

We were wondering if anyone has any advice or suggestions on how to travel with him? It seems some airlines will only allow him to fly with us if he can fit in a small carrier underneath our seat, usually with a weight limit of 20 lbs (he’s too heavy). Others seem to allow him to be placed in cargo, but the plane tickets are double if not triple the amount compared to the others that allow him underneath the seat.

Is there no way to meet in the middle somehow? Is there an airline that will allow him to fly cargo but not have the plane ticket be an outrageous price? It will be about 1.5 hours one way, and he is a naturally calm dog so he will be fine in cargo, if that’s how we need to fly.