A dog traveling on Delta Air Lines with his family from Phoenix to Newark died en route on Wednesday, according to a spokesperson for Delta.  

According to CNN, the dogs owners Michael Dellegrazie and his girlfriend decided to put their eight-year-old Pomeranian Alejandro with cargo. When the plane landed at its layover in Detroit, Alejandro was reportedly still alive, but died during the process of moving him to the couple’s connecting flight. The cause of death is still unknown. "There was a stop in Detroit at 6 a.m. Alejandro was checked on. He was alive. Then between 8 a.m. and 8:30 a.m. he was checked on again and he was dead," said Dellegrazie's attorney, Evan Oshan.

According to Delta spokeswoman Lisa Hellerstedt, the dog’s cage was found with vomit and fluids inside. "The family is very upset," Oshan said. "This is essentially their family member who died. To say they are upset is a gross understatement."

Delta is offering the couple a free necropsy to determine the cause of death. "We know pets are an important member of the family and we are focused on the well-being of all animals we transport," the statement said. "As part of that review, we want to find out more about why this may have occurred to ensure it doesn't happen again."

The news follows United’s recently settled suit with a passenger whose dog died in an overhead compartment. The French bulldog puppy, Papacito, died of suffocation in the air on a flight from Houston to New York after a flight attendant forced his owners to put him in the overhead bin.