Thats interesting. I shipped with them the last week of October I believe. Here is what their site says:

Live animals will no longer be accepted for travel as checked baggage or cargo. US Airways will make an exception for ticketed reservations made before August 17, 2005, to carry pets as checked baggage, which will be honored through November 1, 2005. The policy change does not apply to the transportation of service animals.

As far as Northwest, when I was researching prices, the best they gave me was their warm blooded rate which was around $252.