On Monday, a passenger flying from Houston to New York was told to move her dog, which was in its carrier, from under her seat to an overhead bin. The dog then died in-flight.

In response, United conceded that while “the customer did tell the flight attendant that there was a dog in the carrier,” the flight attendant reportedly “did not hear or understand her, and did not knowingly place the dog in the overhead bin.”

Following extensive backlash on social media, the airline announced that starting in April it will begin issuing bright yellow tags for passengers traveling with pets in carriers to avoid such a mix-up from taking place in the future. While United apologized for the dog’s death, many have called for travelers to boycott United (UAL), and the airline’s shares dropped 2.6% on Wednesday.

This is not the first run-in United has had regarding pets on planes this year. In January, United turned away an emotional support peacock from boarding a flight at Newark Liberty International Airport. The move similarly sparked criticism on social media, pushing United to clarify and further restrict its pet policy. Delta similarly announced tighter regulations for emotional support animals in mid-January.