“It’s just impossible to miss it, you know. I mean, this is not a small gun,” Seif told ABC News. “How can you miss it? You cannot miss it.”

But the TSA did miss it, and despite what most people believe about the painstaking effort to screen airline passengers and their luggage before they enter the terminal, it was not that unusual.

Experts tell ABC News that every year since the September 11 terror attacks, federal agencies have conducted random, covert “red team tests,” where undercover agents try to see just how much they can get past security checks at major U.S. airports. And while the Department of Homeland Security closely guards the results as classified, those that have leaked in media reports have been shocking.