Southwest Airlines says they don't permit any animals onboard. However, on many occasions I've heard more than on few moo's and even one baa while boarding.

Searching for "Livestock" nets you 148 results, Including "Does easyJet carry wheelchairs?" and "Are babies allowed to fly?".

Dead stock... That old bird that popped it on a BA flight wouldn't have had any available assistance.

Having spent a little time up at the pointy end myself, doing a bit of cloud worrying, I can also report that Seat Ballast is also referred to as "Self-Loading Cargo."

While I agree that passengers are treated no better than livestock, I am fairly confident that livestock is not sent by air. Unless you count sheeple.