A bullet hole was discovered by a pilot doing a routine visual inspection before he was set to take off from Charlotte.
He noticed the hole above a window near row 23 on the left rear of the plane.
Closer inspection led agents to believe this was a bullet hole and then sources say the bullet was recovered.
Sources also said it is believed the shot came from a handgun.
It did pierce several layers of the plane, but did not cause any significant damage. But where the bullet came from is still a mystery.

Read more and see video: http://www.myfoxphilly.com/dpp/news/local_news/032911-source%3A-bullet-found-on-philly-plane