A Baltimore County, Maryland, man was arrested Sunday with a loaded 9mm handgun at a BWI Marshall Airport security checkpoint.

According to officials, a Transportation Security Administration officer spotted the pistol in the carry-on bag of the Cockeysville man, who told authorities he forgot he had the loaded gun with him.

Maryland Transportation Authority Police confiscated the gun and cited him on weapons charges. He now faces stiff fines.

So far, six guns have been caught at BWI Airport this year.

Civil penalties for bringing a handgun into a checkpoint can stretch into thousands of dollars, according to a TSA release. Firearms cannot be carried onto a plane, regardless of whether or not someone has a concealed carry license.

However, passengers “are permitted to travel with firearms in checked baggage if they are properly packaged and declared at their airline ticket counter. Firearms must be unloaded, packed in a hard-sided case, locked, and packed separately from ammunition. Firearm possession laws vary by state and locality,” the TSA said.

Penalties are listed online.