Authorities have arrested a Southwest Airlines pilot after a loaded 9 mm pistol was found in his carry-on luggage before he boarded his aircraft at St. Louis' Lambert Airport.

The airport said in a statement that Transportation Security Administration officers made the discovery early Wednesday.

The statement says the 51-year-old pilot didn't have any authorization to carry a firearm on the Las Vegas-bound flight. He was arrested on suspicion of unlawful use of a weapon, and the airline says charges are pending through St. Louis County. A spokesman in the prosecutor's office said no charges had been filed at this point.

Southwest Airlines said in a statement that it's "aware" of the situation and "working alongside the appropriate authorities to gather more information."