United faces possible action by the US Congress, as well as federal and local authorities, along with criticism from passengers after the latest in a series of public relations blunders by the third largest US air carrier.

The most recent incident involved the death of a French bulldog, Kokito, that died last week after a United flight attendant insisted that the puppy's carrying case be stored in the plane's overhead locker during a 3-1/2-hour flight.

Federal and local authorities are trying to determine if there are grounds for legal action in the dog's death, and lawmakers have introduced a bill to Congress that would direct the Federal Aviation Administration to prohibit storing live animals in overhead compartments and establish civil fines for violations.

The district attorneys offices in Harris County, Texas, where the flight originated, and Queens County, New York, where the flight landed, are probing the incident. Both the US Department of Transportation and the Department of Agriculture are also involved.

Social media users have threatened to boycott the airline, with thousands of tweets and re-tweets employing the hashtags #BoycottUnited and #BoycottUnitedAirlines to warn against flying on the carrier.

"You can't talk your way out of a situation you behaved your way into," Anthony D'Angelo, national chair of the Public Relations Society of America, said.

D'Angelo pointed to United's immediate but short public apology to Kokito's owners and other customer relations mishaps, including a mixup last week that led to a Kansas family's dog being shipped to Japan, as evidence of the type of bad headlines that can lead to a reputational "death by a thousand cuts."

"Unless there is a concerted and proactive effort... customers could start asking what's going on. Stockholders could. Legislators could. The board could. At some point you could see some executive changes."

Last April, the careers of some United executives looked in danger after video was published of Chicago O'Hare airport aviation police dragging a bloodied 69-year-old Vietnamese-American doctor from his seat and down the aisle of a parked United plane in order to make room for airline employees.

That incident, and a fumbled initial apology from United Chief Executive Oscar Munoz, prompted severe criticism of the carrier for its customer service shortfalls.

A Morning Consult poll at the time found that 40 percent of respondents said they would spend more time and money to avoid flying the airline.

Pressure has grown on Chief Executive Munoz in the months since to improve customer-carrier relations, and the negative headlines have revealed a number of customer complaints still to be addressed.

'THINK TWICE'

These incidents have attracted the attention of federal legislators to a sector that has operated fairly autonomously since the airline industry deregulation in the 1970's.

After the incident involving the passenger being dragged from the plane, a bill was introduced to the US Congress that would make it illegal for an airline to eject an already-boarded passenger from a flight and require airlines to promptly refund passengers if they do not receive the service they have paid for.

The death of the dog Kokito last week prompted two US senators to introduce the "Welfare of Our Furry Friends Act", or "WOOFF" bill that would impose civil fines for stowing animals in a plane's overhead.

"I would think that anyone that has to travel with United is going to think twice now," Dan Rene, senior vice president of Levick public relations firm, said.

While industry consolidation has limited the number of options US customers have in choosing an airline, Rene warned that United's repeated missteps could even turn cost-sensitive customers off its brand.

That could lead to severed partnerships with other corporations as fewer businesses want to associate with a brand they view as toxic.

"They have to show that they actually care about their customers, and in this case their customer could be on four legs instead of two," Rene said. United needs to "own their current mistakes and talk about what they're doing to make sure it doesn't happen again."

After last year's passenger ejection, United announced changes to the way it would compensate passengers who willingly give up their seats on overbooked flights.

And starting next month, United said it will issue brightly colored bag tags to passengers traveling with in-cabin pets to help flight attendants easily identify the animals.

United declined to comment further on the rash of incidents.