I have the Sherpa travel carrier. I saw a lady on the show, Airplane, this week trying to take a puppy in a non-approved carrier and Southwest would not let her on a 1 hour flight because the carrier did not have an absorbent floor and the puppy could pee and it could leak out!
She was heartbroken and had to leave the puppy behind with her daughter and you could tell it was killing her.
So, for airline travel, Sherpa is Approved. Mine has a pocket on one end that will hold treats, leashes, wipes, poop bags, pills....quite a bit of stuff. I also made a special pad for it out of egg crate foam with a cover of that pee-absorbent material you can get at PetsMart and other places. Over that I put a slip-case of leopard print fleece on one side and the sheepskin fleece on the other. So it's reversible. And I just know he is more comfortable on 3 hour flights than with that hard floor and flimsy sheepskin mat.