The owners, Michael Dellegrazie and his girlfriend, were traveling from Phoenix to NY and made a decision to put their 8-year-old Pomeranian, Alejandro, on a plane so they could pick the dog up at the Newark airport.
"To say they are distraught would be a gross understatement", the family's attorney, Evan Oshan, told WXYZ.
And last Tuesday, a woman traveling from OR to Kansas with her family on a United Airlines flight was stunned when she went to collect her dog from the cargo facility and instead discovered a Great Dane waiting in its place.
Oshan says he's determined to get to the bottom of the incident, so no other family has to go through this pain again.
'There was a stop in Detroit at approximately 6 o'clock in the morning, ' Oshan told ABC News.More news: Trump can probably pardon himself, Giuliani says
"We lost a family member".
Michael Dellegrazie, who owned Alejandro with his girlfriend, said on Good Morning America on Saturday that they followed the airline's rules of having Alejandro undergo a physical before the flight from Phoenix to Newark.
A Delta Air Lines spokesman told Fox News the dog was seen in good health after the flight and brought to the staging area.
Vomit was found inside the crate, according to the spokesperson.
Alejandro's is the latest in a string of pet deaths on board commercial airlines.More news: Isis supporter Husnain Rashid admits plot to kill Prince George
The lawyer represented the owners of Kokito, the French bulldog who was killed on a United Airlines flight in March.
"We know pets are an important member of the family and we are focused on the well-being of all animals we transport".
Delta released a statement saying it is "conducting a thorough review of the situation" and has been working with Alejandro's owners to support them however possible.
"'They had no idea where the dog was", Swindle said. "That's all I can think of", Dellegrazie told CNN.
A day after that incident, a 10-year-old German shepherd named Irgo was flown to Japan when he was supposed to end up in Kansas.More news: Wie has 'a blast' - and 3-under 69 - at US Women's Open
In 2017, 24 of the 506,994 animals transported on US airlines died, according to the Department of Transportation.