Pets in the Hold
 

Yes, pets have died in the hold because the conditions are not very hospitable. Too hot or too cold. I knew a lady whose mother's dog died of heat. Flat faced (braceacephalic) breeds are relegated to flying when the temps are low enough (early for example) in the summer. The airlines where recently required to reveal how many pets have actually died in cargo. I haven't seen the numbers. My pet does ride under the seat in a carrier and no one usually knows she is there. Southwest doesn't allow pets - for those who don't want to fly with them.