Pit bulls have often been blanketed as one breed but there are four different breeds, with each having its own unique characteristics.
"I seen the little girl flat on her back with the bite marks and part of her neck hanging off," eyewitness Deborah Golden said.
Police said the 8-year-old pit bull raced toward officers "like a missile" before they fired shots.
"The safety and security of Delta people and our customers is always our top priority. We will always review and enhance our policies and procedures to ensure that Delta remains a leader in safety."
Police were called and shot dead one of the dogs.
Potential adopters consider them to be as attractive as other dogs if labels are removed, the study says.