On June, 2016, United Airlines flight 1859 landed in Phoenix with a dead Yorkshire Terrier, Diamond, in its cargo hold. Official cause of death was complications due to “cardiac arteriosclerosis.” A month earlier, Pinkerton was also found dead when United Airlines flight 0722 landed in Phoenix — the cause of death in that case was listed simply as “heart failure.”
Those are but two deaths out of a total of nine that United Airlines reported to the U.S. Department of Transportation in 2016, the most of any airline that year. All airlines are required to make these “animal incident reports” of death or injuries to animals on their flights. United reported 23 incidents (deaths and injuries) in total, but they weren’t the only airline to have pets die on their planes.