TSA officers noticed the gun and alerted Philadelphia police officers, who responded quickly, police spokesman Lt. Ray Evers said.
A female police officer, whom the department declined to name, tried to make the weapon safe by removing the bullets but instead accidentally fired it, Evers said. The bullet that was discharged hit the ground and did not injure anyone.
Because the flight attendant, who also was not named, has a valid gun permit, she received only a summary citation for passing the gun through a security checkpoint and was released, Evers said. The flight attendant, however, was replaced by another flight attendant on the Dallas-bound flight, a US Airways spokeswoman said.
The discharge is being investigated by Philadelphia police internal affairs department, Evers said.
"She will go back to training for handling weapons," Evers said of the patrol officer who accidentally discharged the gun. "She will be off the streets for a period of time."
The protocol for such a situation, Evers said, is for a regular patrol officer to respond and if the officer is not sure how to handle the weapon, a police supervisor should be called.
No flights were delayed as a result of the gun discharge, airport spokeswoman Victoria Lupica said.
"Operationally we were business as normal," Lupica said.
Contact Claudia Vargas at 856-779-3917, email@example.com, or on Twitter @InqCVargas.