A man who flew out of Houston's George Bush airport discovered a loaded handgun in his carry-on bag after landing; he'd forgotten he was carrying it and the eagle-eyed TSA screeners were too busy ogling his penis to spot the loaded gun in the nearly empty bag from which he'd dutifully removed his laptop.

"I mean, this is not a small gun," Seif said. "It's a .40 caliber gun."

Seif says it was an accident which he didn't realize until he arrived at his destination. He says he carries the glock for protection but forgot to remove it from his bag. He reported the incident as soon as he landed, shocked at the security lapse.

"There's nothing else in there. How can you miss it? You cannot miss it," Seif said.

Authorities tell ABC News the incident is not uncommon, but how often it occurs is a closely guarded government secret. Experts say every year since the September 11 attacks, federal agencies have conducted random, covert tests of airport security.

A person briefed on the latest tests tells ABC News the failure rate approaches 70 percent at some major airports. Two weeks ago, TSA's new director said every test gun, bomb part or knife got past screeners at some airports.