It's not just under 20lbs, it's the pet plus a hard carrier under 20lbs. Those hard carriers weigh about 5lbs, so your dog needs to be under 15lbs, which means

It's not just under 20lbs, it's the pet plus a hard carrier under 20lbs. Those hard carriers weigh about 5lbs, so your dog needs to be under 15lbs, which means only the smallest of dogs are eligible