United Airlines faced fresh backlash on Wednesday over a puppy that died in-flight after a cabin attendant ordered it stowed in an overhead bin, and the U.S. Department of Transportation said it was examining the events that led to the French bulldog's death.

U.S. Senator John Kennedy, who earlier on Wednesday sent a letter to United Airlines President Scott Kirby demanding information on the high number of animals that have died in the carrier's care, wrote on Twitter that he planned to file a bill on Thursday that would prohibit airlines from putting animals in overhead bins.

"Violators will face significant fines. Pets are family," he wrote.