United Airlines is apologizing after a dog died when a flight attendant made a passenger put her pet carrier in an overhead bin.

The incident happened Monday night on United Flight 1284 from Houston to New York's Laguardia Airport.

According to multiple passenger accounts, a mother and her two children boarded the flight to New York City with their French bulldog in a carrier when a flight attendant told them to put the bag in the overhead bin.

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"The passenger adamantly refused but the flight attendant went on with the instruction," passenger Maggie Gremminger wrote.

Passenger June Lara explained that the flight attendant "assured the safety of the family's pet so wearily, the mother agreed."

When the flight landed, they discovered the puppy had died.

"I assumed there must be ventilation as surely the flight attendant wouldn't have instructed this," Gremminger added.

In response, United released a statement apologizing for the dog's death and promising an investigation.

This was a tragic accident that should never have occurred, as pets should never be placed in the overhead bin. 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.

USA Today found that United Airlines accounted for one-third of U.S. animal deaths aboard passenger flights during the last five years.

Story courtesy of 9news.com.