http://www.nbc5.com/travelgetaways/2662716/detail.html
According to NBC5 tv news:

An Oregon family said their cat died because it was not allowed to be carried
on with their other two felines. Sara Stano said her family chose Delta
Airlines because they assured her their three cats would be allowed as carry-on
luggage. Instead, Stano said, the family was allowed to carry on only two cats
and had to check the third one.

When they arrived in Greensboro, N.C., the cat in the cargo hold was dead.
"They brought him out in his kennel, and they sat him down next to us, and he
was dead," Stano said. "He had been dead awhile. He was really stiff, and he
was really cold. It was horrible," Stano said.

Delta Airlines did not comment on the cat's death, but their guidelines state
that passengers assume full responsibility for animals that are transported. -
story end.

I think this is horrible, but I think the family dropped the ball. They should
have relied less on the assurance of a telephone sales agent or travel agent
and received a confirmation IN WRITING. After all, three cats were to be
travelling. In addition, why didn't the family refuse to board and demand
intervention by a very senior airline executive to try to work this out? Also,
if passengers are legally allowed to bring at least one carry one piece of
luggage, then why wasn't each family member allowed to designate one cat
carrier as their designated piece of carry on luggage?

I will personally contact Delta for these answers and hope y'all do as well? If
Delta did cause the death, I hope everyone boycotts the airline!