Originally Posted by
baccarat_king
It is blocked at reservation (i.e. a restriction is placed, when you add "pet in cabin, international")
from delta.com:
First Class /Business Elite / Business Class Restriction
Pets in Cabin are not allowed in the First Class/ BusinessElite / Business Class cabin on any international segment, regardless of aircraft type due to insufficient space.
It's a space issue, DL says it themselves, and the OP quoted it. Dog carrier will not fit under the seats in BizElite. You can't have it at your feet for take off and landing, and can't put it in the overhead bin. You *might* be able to get a very small one in the footwell of some of the flat beds, but there is absolutely no space to put it under the older style sleeper seats.
I am sure it has nothing to do with yappy dogs annoying business class passengers.