United Airlines has suspended its animal shipment services while it conducts an internal investigation into its PetSafe travel program, the company said in a statement Tuesday.

The airline will no longer accept bookings to transport animals as cargo — though it will honor any shipments that have been booked prior to Tuesday.

Passengers will still be allowed to bring small animals in portable carriers in the cabin of the plane.

United Airlines has drawn intense scrutiny in the past week, after a German shepherd was mistakenly shipped from Oregon to Japan, rather than its intended destination of Kansas City, Mo. The dog was being transported as part of United’s PetSafe program, designated for animals that cannot be brought into the cabin inside a carrier, and must instead travel in the cargo hold.

(A similar incident occurred last week on Delta when a puppy headed to Idaho was mistakenly flown thousands of miles around the country, landing in at least four other states before reaching his destination.)

The German shepherd was ultimately returned to its family.

But that high-profile incident only exacerbated United’s public relations crisis, after a 10-month-old French bulldog died on-board a Houston-New York City flight on March 12. A flight attendant demanded that the dog’s carrier be stored in the overhead compartment of the plane. He apparently suffocated during the three-hour trip.

The bulldog puppy was not traveling as part of the PetSafe program, but the animal’s death — and the ensuing social media ire — prompted federal officials, criminal investigators, lawmakers, and animal-rights advocates to ask tough questions of United and its poor record for safely transporting animals.

Of the 24 deaths of animals that occurred on major U.S. air carriers last year, 18 occurred on United.

In a statement posted Tuesday on the company’s website, United said it was temporarily halting its PetSafe program in order to “make improvements” that will better protect the safety of animals traveling as cargo on its planes.

“We are taking this voluntary action to conduct a thorough and systematic review of our PetSafe program and make improvements that will ensure the best possible experience for our customers and their pets,” the statement said.

According to United’s statement, the company expects to conclude its internal review by May 1. It is unclear how quickly the airline will restart its pet shipment program after the conclusion of the review.

For those who have an existing animal shipment reservation with United, the company also said it will “assist any customer that wishes to cancel their reservation.”

Last week, United also announced that it will start issuing “bright colored bag tags” for passengers bringing small animals into the cabin of airplanes.

In the aftermath of the French bulldog’s death, the flight attendant who ordered the dog’s carrier into the overhead compartment told United officials she was not aware that there was a live animal inside the carrier. Still, other passengers on the plane said that the dog’s owner alerted her several times that there was a dog in the bag.

“This visual tag will further help our flight attendants identify pets in-cabin,” the company said.