A hole in a US Airways jet that landed in Charlotte, North Carolina, on Monday was caused by a bullet, two government sources tell CNN.

The sources say a bullet has been recovered inside the Boeing 737-400.

The aircraft had flown to Charlotte from Philadelphia and was being prepped for another flight on Monday when the pilot discovered the hole above a passenger window toward the back of the plane, according to airline officials. The airline pulled the plane from service and called in the FBI.

"We do not believe it's terrorism related," said one of the government sources. "It appears to be a random event. We do not believe the plane was targeted."

One source told CNN that officials believe the bullet was fired in Charlotte after passengers had exited the aircraft.