The big problem is that anyone can refuse to take your fish at the gate. I called the airline twice before crating up my fish for a relo and was told, twice, that it's OK to check in my fish so long as I agree to pay for over-baggage. When I arrived at the airport, all the boxes were tagged. As I was ready to pay the extra baggage fees, a manager came out and said that they were going to return the boxes since they were no longer going to allow the fish on my flight.
I had to rent 2 carts, rebook my flight, and push/walk my 14 fish boxes and luggage to the airport post office on the other side of the airport (I was dropped of at the airport so, didn't have a vehicle). The post office was going to refuse to ship but, the manager took pity on me (he has a few tanks himself). So, $920 later, my fish were off on airfreight.
Unfortunately, alot of my boxes were redirected. Of the ones that didn't arrive in MS with me, several wound up in Chicago, which caught up with me a week later (of course, the fish didn't make it). A couple of other boxes went from Oregon to Salt Lake city to Chicago to Michigan to Ohio and finally to Houston. The boxes were never seen again since arriving in Houston.
BTW, one of the boxes that made it to MS with me was crushed by a bag car tow tractor and crushed to death one of my female FRTs.
Final note; Paying additional fees for insurance only covers the shipping costs. No airline or package carrier will honor any claim concerning any loss of a living shipment. In order to be covered, you have to buy insurance on your own as you would your own health insurance.