Originally Posted by
redreeper
It is my understanding that on US airlines pet cannot be shipped in the baggage area, only as cargo, between 5/15 and 9/15 but please correct me if I am wrong.
You are wrong, yes.
Certain breeds of pets cannot be shipped in in the hold at all during the summer months, yes... but the restriction is limited only to certain breeds (short-nosed breeds who could have trouble with hot weather) and is for both checked baggage and cargo (they both go in the same place).
Originally Posted by
redreeper
That may answer your question as to why the animal was in the cabin and not checked as baggage
Not in this case, since based on the description the dog was normal- or long-snouted, which is usually the case for service dogs.