Officials with the Transportation Security Administration say they already have implemented changes in order to fix the dismal showing of their agents during a routine undercover audit at several of the nation’s busiest airports. Earlier this week, the Department of Homeland Security reassigned the acting director of the TSA.

We hope this time, at last, the changes will actually make a difference.

The audit showed TSA agents failed to catch people with fake explosives or weapons 67 out of 70 times. Once, a machine triggered an alert when an undercover agent passed through with a device attached to his back. However, a subsequent pat down failed to detect the device, and the undercover agent was allowed to proceed to his gate.

Whatever new procedures have been implemented, Americans can be excused for having little faith in their effectiveness. The nation’s many air travelers may feel a sense of security given that terrorists have been unable to successfully hijack an aircraft in the United States since 2001, but it is a sense built on false assumptions.

The newest undercover tests were not much different from previous tests. According to an ABC report, a similar test in 2006 in Newark failed to detect concealed bombs and guns 20 out of 22 times. In Los Angeles in 2007, inspectors had a little better time of it. They missed only 50 out of 70 times.

Amid these disturbing results, the administrator of the TSA in 2013 implied the tests weren’t fair. The undercover agents know everything about the agency’s protocols and were experts at exploiting its weaknesses, he said. They could do so in ways “not even the best terrorists would be able to do.”

We can see plenty of problems with that way of thinking. The first is that there is plenty of evidence to suggest trained agents aren’t the only ones getting through security with their weapons intact.

Last year, the TSA reported a 22 percent increase in the number of firearms confiscated at checkpoints. But some travelers report accidentally carrying guns with them, out of habit, and discovering at their destination that they had carried the weapons throughout the trip, undetected.

One such man, Iranian-American businessman Farid Seif, reported carrying a snub nosed "baby" Glock through security in Houston a few years ago, unaware he was carrying the weapon.

The other problem is that there is little reason to doubt real terrorists are capable of learning protocols in an effort to exploit weaknesses. Among the many lessons of 9/11 was a warning not to underestimate the lengths to which the nation’s enemies will go to carry out a mission, even undergoing pilot training.

Last year, former TSA agent Jason Edward Harrington caused a stir by publishing an op-ed on about the agency’s problems. While most of the attention was riveted on his assertions that agents retain the images of certain people who pass through full-body scanners in order to make fun of them in private, he also described how ineffective such machines are in catching terrorists.

He wrote, “Officers discovered that the machines were good at detecting just about everything besides cleverly hidden explosives and guns.”

Utah Rep. Jason Chaffetz has suggested changing methods at airport checkpoints, perhaps adding dogs that could wander through waiting passengers, sniffing for explosives.

Whether this would make flying safer is uncertain. What seems more certain, however, is that the TSA has not been serious enough about responding to its repeated failures on undercover tests.