[Butch Cassidy Slept Here]

You should report any airline to the ASPCA which would accept animals and could not guarantee their comfort and safety.

To my understanding some airlines, American MAY be one, simply refuse to accept animals, under any circumstances, for travel in the cargo hold. I believe the decision to accept, or not accept, animals (with the exception of bona fide service animals traveling in the passenger compartment) is entirely up to the airline, at least for domestic passengers. The DOT decision to start keeping stats on animals that die during travel in the cargo hold may be one reason for American's decision. Of those airlines still accepting animals for cargo hold travel some will not accept them when there are extreme temperatures at either the departure, connecting or arrival airports. I believe the cargo hold CAN be heated in flight.