LONDON — Call it the curse of O’Hare.

Less than three weeks after a passenger was dragged off a United Airlines flight at the Chicago airport, the carrier found itself facing another public relations fiasco on Wednesday after a three-foot-long rabbit died on a flight from Britain.

The continental giant rabbit, Simon, which was bound for O’Hare, had a veterinary checkup three hours before takeoff from Heathrow Airport near London and was “fit as a fiddle,” his breeder said. The animal was traveling to a buyer in the United States.

Continental giants are an ancient breed, descended, appropriately enough, from Flemish giants. They are known to be gentle, friendly and intelligent, as rabbits go. An enthusiasts’ website says the giant makes “a fantastic house rabbit” but that “cables, wires, shoes, papers and anything important” should be kept out of its way, as it will chew them to bits.

Simon’s death remained a mystery on Wednesday. “Something very strange has happened, and I want to know what,” the breeder, Annette Edwards, told the British tabloid The Sun.