Airlines' definitions of "medium" and "large" kennel?
 

What are the airlines' definitions of "medium" and "large" kennels for transporting pets as checked cargo/baggage? My main interests would be domestic *A carriers (UA, US, soon-to-be CO), but I haven't had much luck on airline websites finding definitions, and I suspect that all the USA carriers use the same or similar definitions.

We've got a 33" * 22.5" * 24" kennel for our dog. He could probably fit in one an inch or so smaller in each dimension if that would classify it as medium. (No plans to travel with our dog right now, but there is a local sale on pet carriers.)

I don't know how much the following will help, as it pertains to AA, but I suspect (as you do) that all USA carriers have similar requirements:

Pets Traveling as Checked Baggage

The maximum size for checked kennels is a series 500 kennel with the following dimensions: 40" long x 27" wide x 30" high. However, this size kennel is not accepted on the Boeing MD-80 (S80). Kennels checked on MD-80s must be able to fit through the cargo door while remaining in an upright position. MD-80 cargo doors are 29" high x 53" wide.

Series 700 kennels are not allowed on any aircraft.

The maximum weight of a checked pet and kennel (combined) cannot exceed 100 lbs.

Collapsible Kennels (those which can fold down flat) can not be accepted due to the risk of collapse during transport.

Pets Traveling as Carryon

The maximum size for cabin pet carriers is 23" long x 13" wide x 9" high.

i flew with my dog many times,,,as a puppy also,they told me to have a health certificate. funny they never even checked it. but to be safe i would get one.