ROMULUS, Mich. (AP) — Delta Air Lines is investigating the death of an 8-year-old pet dog during a layover at Detroit Metropolitan Airport, en route from Phoenix to Newark, New Jersey.

The Pomeranian, called Alejandro, was found dead Wednesday morning in its carrier in a cargo facility at the airport, southwest of Detroit in Romulus.

"When he landed here in Michigan, he was alive at 6:30 a.m., and then at 8:20, he wasn't moving and it just doesn't make any sense to me," owner Michael Dellagrazie told WDIV-TV. "We lost a family member. That's exactly what happened, and somebody has to be responsible for it. He was in their care and they didn't take care of him."

Delta told WXYZ-TV that a flight attendant checked on Alejandro about 6 a.m. The attendant checked again about two hours later and the dog was dead.

The airline is "conducting a thorough review of the situation to find out more about why this may have occurred to ensure it doesn't happen again," Delta said in a statement.

The Dellagrazie family is being represented by attorney Evan Oshan. He also represented the owners of a French bulldog puppy that died earlier this year after a United Airlines flight attendant ordered the dog's carrier to be stowed in an overhead bin.

"I think this stretches beyond just pets," Oshan told WXYZ-TV. "I think this is the way that airlines, commercial airlines in general, treat people. They are treating people horribly."

United Airlines stopped its pet-shipping business in March after several dogs were put on wrong flights, but plans to resume shipping pets as cargo in July. United said in May that it only will accept dogs and cats. It will ban 25 breeds including pit bulls, boxers, bulldogs, pugs and Persian cats. The changes don't affect pets in the cabin.

The French bulldog that died in March was not part of the cargo program.

In 2017, 18 animals died on United, three-fourths of all such deaths on U.S. airlines. United cited its willingness to carry riskier breeds barred from other airlines.