LONDON, United Kingdom (AP) — United Airlines is investigating the death of a giant rabbit on one its trans-Atlantic flights, adding to a growing list of customer complaints for the US carrier.

Distraught breeder Annette Edwards told The Associated Press by phone Wednesday that a veterinarian checked Simon, a 10-month-old, 3-foot (meter)-long continental rabbit, shortly before the animal was put on a flight from London’s Heathrow airport to Chicago’s O’Hare. Simon had been purchased by a celebrity whom Edwards did not identify.”Simon had his vet check just before getting on the plane,” she said. “He was fit as a fiddle.” The airline said it was “saddened” by the news and had been in contact with Edwards to offer assistance.”The safety and wellbeing of all the animals that travel with us is of the utmost importance to United Airlines and our PetSafe team,” the airline said in a statement.Edwards said the airline was examining CCTV images to determine what happened to the rabbit. United declined to comment on the matter beyond its statement.United had the second-highest level of animal deaths and injuries of any US airline last year, or 2.11 per 10,000 animals transported, according to US Department of Transportation figures. Only Hawaiian Airlines was worse at 3.99, the result of three deaths among the 7,518 animals transported.United reported nine deaths and 14 injuries for a total of 23 incidents, the highest figures for each category among US carriers. The airline transported 109,149 animals last year, second only to Alaska Airlines with 112,281. Alaska reported two deaths and one injury.United is already working to repair its image after a passenger who would not give up his seat on an overbooked flight was dragged forcibly from a plane at O’Hare Airport in Chicago.Airport security officers removed David Dao, a 69-year-old from Kentucky, from the United Express flight. Images of his bloodied face were widely circulated on social media, forcing United CEO Oscar Munoz to apologize.Two weeks earlier, United was criticised after a gate agent stopped two young girls from boarding a flight because they were wearing leggings. The airline said leggings violate the dress code of the United Pass program, a benefit for employees and their dependents, under which the girls were flying.The airline said last week that Munoz would not automatically become chairman of the carrier’s parent company, United Continental Holdings, next year as originally planned.Munoz was widely faulted for his early responses to the incident where the passenger was dragged off the plane. He first blamed the passenger but later apologised repeatedly for United’s handling of the situation.