I was bypassing screening (again on official FBI business) with my .40 caliber semi-automatic pistol, and a TSA officer noticed the clip of my pocket knife. "You can't bring a knife on board," he said. I looked at him incredulously and asked, "The semi-automatic pistol is okay, but you don't trust me with a knife?" His response was equal parts predictable and frightening, "But knives are not allowed on the planes.