By (Reuters) New York – United Airlines is resuming the shipment of pets in its airplane cargo holds, the carrier said on Tuesday, after having paused the program for improvements following the high-profile death of a puppy on one of its flights earlier this year. United, the third-largest US airline by passenger traffic, said it is partnering with the American Humane animal rights organization to improve the well-being of the pets it flies, after a spate of animal-related mishaps. "As we continue our review process to ensure that we are always doing what's right, we are committed to making significant improvements in our program," United Vice President of Cargo Jan Krems said in a statement. United suspended cargo pet transport in March after a puppy died when an attendant forced its owner to stow the dog's carrying case in an overhead bin. In the days after, United again made headlines for flying two dogs to the wrong locations. According to the US Department of Transportation, of the 24 animals that died on US carriers last year, 18 were on United flights. The animal problems compounded a public relations nightmare for United tracing back to last year, when a passenger was pulled from his seat and dragged down the aisle of a parked United plane in order to make room for an airline employee. Effective June 18, the Chicago-based airline will only accept cats and dogs in its PetSafe transport program, and no other household pets. Short- or snub-nosed cat and dog breeds, like French bulldogs – the breed of the dog that died in the overhead bin – and strong-jawed dog breeds, like Mastiffs, will no longer be permitted to fly as cargo. United's policy changes reflect a growing trend of airlines tightening restrictions on what animals they will fly, following a spike in animal transport requests. Rival Delta Air Lines earlier this year announced it would impose stricter requirements after what the carrier said was a 150 percent increase in service and emotional support animals – pets, often dogs, that accompany people with disabilities – carried onboard since 2015. American Airlines has also said it is examining its policies surrounding onboard animals. US carriers have looked to the federal government to impose universal requirements on what animals passengers are allowed to fly.