Travelers are screened by Transportation Security Administration workers at a security check point at Chicago’s O'Hare International Airport on June 2, 2015. The acting head of the TSA was replaced following a report that airport screeners failed to detect explosives and weapons in nearly all of the tests that an undercover team conducted at airports around the country. (Scott Olson/Getty Images)

Last week, agents at U.S. airport security checkpoints intercepted 45 guns, an assortment of knives and brass knuckles, and several deactivated hand grenades. Two weeks ago, the count was 53 guns, and the week before that, it was 57. And if you’ve ever tried to slip through with a bottle of water, well, you probably got caught.

This week, the acting head of the Transportation Security Administration got bounced from his job because in 95 percent of test cases, real guns or fake bombs made it past the TSA.

That left some travelers asking whether it’s safe to fly and others wondering whether security measures they often find strict and intrusive are as lax as those test results suggest.

“The bottom line remains that it’s just completely unacceptable to have such a high failure rate,” said John S. Pistole, who led the TSA for four years before resigning six months ago to become president of Anderson University in Indiana.

The undercover testing was done by agents dispatched by the Department of Homeland Security’s inspector general, John Roth. They reportedly outwitted TSA checkpoint officers 67 out of 70 times this year, passing through with undetected weapons and phony explosives.

Homeland Security Secretary Jeh Johnson has reassigned the TSA's acting administrator following security failures at U.S. airports. (Reuters)

Little else is known about how, where or when the tests were conducted. Alarmed by the findings, Roth rushed them to Homeland Security Secretary Jeh Johnson. The results won’t be compiled into a written report for another month and, given that they expose vulnerabilities in the system, the document isn’t likely to be formally released.

Pistole came to Washington to discuss the matter with Roth and Johnson. While he declined to describe its specifics, he did provide context for interpreting the information before flying home Wednesday.

Without excusing the failures, Pistole said that members of the inspector general’s “Red Teams” sent out to do the testing have several advantages that would-be terrorists, in particular, and pistol-packing passengers do not. Because he didn’t have the specifics of the 70 tests, Pistole talked in general about Red Team tactics.

“They have the benefit of knowing what the [TSA] detection capabilities are — literally the specifications on each type of machine they’re trying to test,” he said. “They know what the [TSA’s standard operating procedures] are. They know what the training is for the [TSA officers], and they know what the response protocols are. So couple that with the fact that they can devise and construct and conceal these devices with the luxury of not having to worry about a [military] drone overhead or they’re not out in a hut in Yemen someplace.”

Pistole came to the TSA as a career FBI agent and immediately set out to transform it from a wall of airport security guards into an intelligence-reliant agency. When terrorists try to sneak into the country or onto U.S.-bound flights, there is a terrorist watch list. When plots are hatched, there are informants and a vast network of communication intercepts.

“Compared to a real-life terrorist situation, what’s missing from these covert tests is the ability to collect any intelligence,” Pistole said. “That is often the most important part of detecting and deterring a putative terrorist. When you take out the whole intelligence element of it, it really skews their ability to get through.”

He pointed to a pair of bombs built in Yemen and bound for the United States in 2010 that were intercepted based on Saudi intelligence. And in 2012, the second terrorist to attempt to use an underwear bomb, Ibrahim al-Asiri, was foiled by a double-agent inside al-Qaeda’s Yemen branch, he said.

“That being said, there’s no way [the Red Team] should be getting through as much as they did,” Pistole said. “Did the technology work properly? Were the [standard operating procedures] adequate for what the evolving threats were, and how did the officers behave?”

Pistole said Johnson would look at all three areas.

“Is there a pattern of new employees, or are they senior officers and they’ve been on the job 12 years and maybe they’ve become complacent?” Pistole said. “Then you look at the technology. When was the last time the machines were recalibrated? Are they performing to specifications? All those things form part of that context in looking at this.”

The upside of findings that cost acting TSA administrator Melvin Carraway his job on Monday will come when the inspector general’s report is complete and can be used to train front-line TSA airport officers, Pistole said.

“Just seeing some of the concealment techniques that the IG used, that will really be helpful for the security officers who will think, ‘Oh, okay, so that’s how they did it,’ ” he said.