London: A giant rabbit almost a metre long has died on a United Airlines flight from London, weeks after the airline faced a global backlash over its treatment of a passenger who was dragged from his seat.

The 10-month old rabbit named Simon, who was tipped to become one of the world's largest rabbits, was travelling to O'Hare International Airport in Chicago from Britain after a celebrity owner bought him.

He was healthy before the flight, the rabbit's breeder said.

"Simon had a vet's check-up three hours before the flight and was fit as a fiddle," breeder Annette Edwards told The Sun newspaper.

"Something very strange has happened and I want to know what."

The continental giant breed rabbit died in the cargo section of a Boeing 767 after leaving Heathrow, she said.

"I've sent rabbits all around the world and nothing like this has happened before," Edwards was quoted as saying.

"The client who bought Simon is very famous. He's upset."

United spokesman Kevin Johnston said in an emailed response: "We were saddened to hear this news.

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

"The safety and wellbeing of all the animals that travel with us is of the utmost importance to United Airlines and our PetSafe team."

Earlier this month, a United passenger, David Dao, was dragged from his seat off a parked plane at O'Hare International Airport to make room for crew members.

Video recorded by other passengers showed Dr Dao, 69, being dragged down the aisle with blood on his face after refusing to give up his seat on the flight.

Reuters