their flight plan and also to try to figure out how or why this could have happened. linsey. thinking about all of those involved. mireya, thank you. we turn to the box cutter scare aboard a frontier airlines flight. the suspect allegedly threatened passengers causing the plane to make an unscheduled landing. now the urgent questions about how this could happen. here is phil lipof. come on. reporter: tonight, the tsa sending some agents back to training after a man boarded a frontier airlines flight in northern kentucky with two box cutters, and reportedly threatened to harm other passengers. how did he get a knife on a plane? reporter: the tsa admits the agents didn t follow standard operating procedure, missing a box cutter in the man s backpack, after screening it for explosives, but finding another. and according to the agency, the visible blades were removed from the box cutter and provided back to the passenger. once on the plane, passenger ben mutz, an active duty