United Airlines is suspending new reservations for cargo-hold pet transportation as it reviews this business, following a wave of negative publicity after the death of a puppy on board and mix-ups involving several dogs sent to the wrong destinations.

Last week, United apologized for the death of a passenger's dog after its carrier, with him inside, was put in an overhead bin. Following the death of French bulldog Kokito, the airline said there were several mixups that sent dogs to the wrong destinations, including a German Shepherd it mistakenly sent to Japan. The incidents are the most recent of United's public relations disasters since last April, when passenger David Dao was violently dragged off a flight to make room for commuting crew.

The suspension will not impact pets traveling in the cabin. Following the puppy's death last week, United said it would require bags containing animals in the cabin to attach a brightly-colored tag to the carrier to prevent animals from being placed in overhead bins. The airline said a passenger told a flight attendant, who insisted the bag be put in the overhead bin, that a dog was inside the bag but said the flight attendant did not hear or understand her.

United Airlines transports more animals in the cargo hold than any other U.S. airline, according to Department of Transportation data. That is partly due to an animal-transportation business it inherited from Continental Airlines, when the two merged in 2010.

The airline will honor reservations made by Tuesday for pets scheduled to fly in the cargo hold, but will not accept new reservations, pending a review.

United said it expects to complete the review by May 1.

"We are conducting a thorough and systematic review of our program for pets that travel in the cargo compartment to make improvements that will ensure the best possible experience for our customers and their pets," said United spokesman Charlie Hobart. "To achieve this outcome, we will partner with independent experts in pet safety, comfort and travel."

United and other airlines have struggled to handle an onslaught of animals traveling with the airline. In March, United and Delta started requiring customers with emotional support animals to bring more documentation about the animal's health and training after a rash of incidents including biting and soiled cabins.