United Airlines is still investigating the origins of a giant rabbit's death following its trans-Atlantic flight. Reuters

In the evolving case of Simon the rabbit — potentially the world’s largest bunny who was said to have died on a flight from the U.K. to the U.S. earlier this week — a spokesperson for United Airlines offered an update on the matter.

According to a United Airlines spokesperson, 10-month-old Simon died after the United flight plane he was traveling on landed in Chicago, CBS News reported Thursday.

Prior reports released Wednesday said that Simon died during the trans-Atlantic United flight. Simon’s breeder, Annette Edwards, a former glamor model, argued that she had taken the rabbit to the vet for a check-up prior to his departure.

“Simon had a vet’s check-up three hours before the flight and was fit as a fiddle,” she told the Sun.

United said they would investigate the incident.

“The safety and wellbeing of all the animals that travel with us is of the utmost importance to United Airlines and our PetSafe team,” United had said in a statement.

In a follow-up, United spokesperson Charles Hobart stated that Simon arrived at O’Hare airport alive and healthy. It was around half an hour later while awaiting his second leg that Simon appeared to be ‘sleeping’ to employees at the company’s pet facility. Now, the airline is investigating how the animal was handled following his flight departure.

Simon was actually en route to his new home in the United States; his final destination was Kansas City, as he was bound for the Iowa State Fair, according to KCCI. Bryan Bergdale, a farmland investment manager, was to be Simon’s “chief caretaker.” The rabbit was purchased for about $530 and was set to appear at the state fair, according to the outlet. Simon, somewhat of a celebrity mammal, was slated to be the next world’s largest rabbit. He was the offspring of Darius, a Guinness World Record-winning rabbit for his size of about four feet.

“We won’t know the cause of death because we offered to perform a necropsy free of charge – that’s standard procedure – but the customer didn’t want us to perform a necropsy, and we understand,” Hobart said of Simon’s death, according to CBS News.

“We’re still in the mourning process,” Bergdale said of the rabbit’s death. “We’re not quite sure what we’re going to do.”

Initially, when the rabbit was reported to have died in the cargo hold of the plane en route to his layover destination at O’Hare, PETA issued a statement to United Airlines CEO Oscar Munoz admonishing the airline for its treatment of animals.

“Animals aren’t cargo. Dogs, cats, and other animals often sustain significant injuries or even die when they are tossed around in carriers and treated as such,” PETA President Ingrid Newkirk wrote in her letter.

Indeed, United Airlines was ranked as having one of the highest numbers of total incidents involving the death or injuring of an animal during air transportation in 2016, according to the U.S. Department of Transportation. Out of about 109,000 animals transported last year, it reported nine animal deaths and 14 injuries.