The decision comes after a number of recent mishaps involving pets on United flights. In the past few days, the airline put several dogs on incorrect flights, and earlier this month, a puppy died on a flight after a flight attendant told its owner to stow it in an overhead bin.

The program’s suspension does not affect pets that fly inside cabins. However, only pets that fit in carriers placed under seats qualify. Starting in April, United will start placing bright tags on pet carriers transported inside airplane cabins so that they are more easily recognized by crew members.

The suspension of PetSafe doesn’t apply to existing reservations. It only prevents customers from making new reservations for their pets.

“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,” United said in a statement. “To achieve this outcome, we will partner with independent experts in pet safety, comfort and travel.”

United says it expects to complete its review by May 1, at which time reservations will likely once again be accepted.