"Over the course of our history, passengers have usually brought about two guns a day to airports around the country. In the last seven days, we've seen four guns at two airports here in Southern California," TSA spokesman Nico Melendez said.
It happened twice last week at Ontario International Airport. It also happened once Tuesday and once Friday at Los Angeles International Airport.
"Most times, passengers just say to us, 'I forgot it was there,'" Melendez said. "We constantly ask passengers do your due diligence, look through your bag."
Checking in a firearm is legal, as long as it is unloaded, stored inside a proper carrying case and declared to the airline. That was not the case in any of the four incidents in the last week.