CHICAGO - Simon, a giant bunny on his way to becoming the world's biggest rabbit, was found dead in the cargo hold of a United Airlines plane earlier this week.

The 90cm-long continental giant rabbit, aged 10 months, was travelling from London's Heathrow to the O'Hare International Airport in Chicago, media reports said.

He was found dead upon arrival at O'Hare, the scene of the worst public relations disaster for United two weeks ago when passenger David Dao was filmed being dragged off an overbooked flight.

Simon was reportedly the son of Darius, the world's largest rabbit at 1.3m long.

He was said to be well on his way to overtaking his father in the size stakes, and was being sent to his new "celebrity owner", who is reportedly considering legal action.

The owner's identity was not revealed.

United said in a statement to the BBC that it was "saddened" by the rabbit's death.

"The safety and well-being of all the animals that travel with us is of the utmost importance to United Airlines and our PetSafe team," it added.

"We have been in contact with our customer and have offered assistance. We are reviewing this matter."

Simon's owner, Ms Annette Edwards, told the Sun newspaper that he was "fit as a fiddle" after having a check-up three hours before his flight.

"Something very strange has happened and I want to know what. I've sent rabbits all around the world and nothing like this has happened before," she said.

Ms Edwards is a glamour model-turned-rabbit owner who reportedly hires out her rabbits at £500 (S$893) a time.

The latest incident caps a torrid few weeks for United, who has faced global backlash over its handling of the case involving Dr Dao.

United has since apologised for its handling of the April 9 incident and is reviewing its policies on overbooking planes.

US Department of Transportation figures in 2015, the latest data available, showed that US airlines reported 35 animal deaths that year.

Fourteen deaths occurred on United flights, with another nine injured.

The airline carried 97,153 animals that year, meaning its rate of 2.37 incidents for every 10,000 animals transported was the highest rate seen on any US airline.