Another passenger, Maggie Gremminger, told People a flight attendant told the dog owner to move the carrier her dog was in.
"The flight attendant told the passenger that her bag was blocking part of the aisle. I could not see it, as I was already in my seat, but it sounded like it was somehow not completely fitting beneath the seat in front of her," according to Gremminger. "After the flight attendant asked her to move it above, the woman adamantly refused, communicating her dog was in the bag. There was some back and forth before finally the flight attendant convinced her to move the carrier to the bin above."
Gremminger said the dog was barking from the overhead bin for at least 30 minutes but was dead by the time the owner went to get the dog when the plane landed.
According to social media posts from Laura and Gremminger, the flight was from Houston's George Bush Intercontinental Airport to LaGuardia Airport in New York. The flight was nearly 4 and half hours.
United Airlines issued the following statement about the incident:
"This was a tragic accident that should have never occurred, as pets should never be placed in the overhead bin," United said in a statement. "We assume full responsibility for this tragedy and express our deepest condolences to the family and are committed to supporting them. We are thoroughly investigating what occurred to prevent this from ever happening again."
The Department of Transportation lists United as having the highest rate of airline reports on incidents involving loss, injury or death of animals during air transportation. Of 40 total incidents involving animal loss, injury or death in 2017, 18 incidents involved an animal's death on United Airlines.
A spokesperson for United could not say if anyone had been disciplined in relation to the incident.