It is highly questionable if the dog should have been accepted for travel in the first place. We already know short nosed breeds have issues travelling as cargo, hence they should be Pet in Cabin, having said that, Pugs, Peeks just about fit in the flexible bags under the seat, unless it is a pup, I doubt a French Bull Dog would fit without a loot of squashing and you can't blame the pet for barking. Was the dog shown at check in? or was it on the lead and the staff shown an empty bag? I have personally seen pax moved around so these dog issues can be resolved, but on a full aircraft its tough. In any event, putting a live animal in the OHB is reckless. Quote: "We have learned that the customer did tell the flight attendant that there was a dog in the carrier. However, our flight attendant did not hear or understand her, and did not knowingly place the dog in the overhead bin," United said in the statement. "As we stated, we take full responsibility and are deeply sorry for this tragic accident."
Incidentally, we do not allow pet in cabin and baby to travel in the same row.