You've certainly heard by now about the tragic death of a pet dog that suffocated on a United Airlines flight from Houston to New York City earlier this week after its owner was forced by a flight attendant to move the dog (in its TSA-approved pet carrier) into an overhead storage compartment. Unfortunately, this is not the first time a pet has died on a United Airlines flight, and it likely won't be the last.

While deaths of pets on airline flights are a relatively rare occurrence, four U.S. based airlines reported pet animal deaths, injuries, and losses in 2017.

And at the head of the pack? United Airlines.

According to U.S. Department of Transportation statistics, in 2017, a total of 24 pets died on U.S.-based airline flights. Of these 24 deaths, 18 -- fully 75 percent -- were on United Airlines flights, double the number reported by the airline in 2016. Not only that, but 13 of the 15 pets injured on U.S.-based airline flights in 2017 were on United Airlines.

Out of a total of 40 incidents reported by U.S.-based airlines in 2017, 31 took place on United Airlines flights. To compare, Alaska Airlines, Delta Air Lines, and American Airlines reported just 3 pet incidents each in 2017 (including 2 pet deaths each).

With the public in an uproar over the treatment of animals by airlines -- first the fake companion/support animal controversy, and now the death of pets -- politicians have begun to notice, and they are taking action.

Louisiana Senator John Kennedy has written a letter to the president of United Airlines, J. Scott Kirby, demanding answers. In his letter, Kennedy said,

"For many people, pets are members of the family. They should not be treated like insignificant cargo. Frankly, they shouldn't be placed in the cargo hold much less an overhead bin."

In a tweet, Kennedy went on to say that he would sponsor a bill prohibiting airlines from putting animals in overhead bins.

For its part, United Airlines -- which took "full responsibility" for the dog death incident this week -- now states that the flight attendant in question did not "hear or understand" that there was a dog in the pet carrier.