Response to TSA Proposal to use AIT

In regard to Docket Number TSA-2013-0004:

The TSA’s proposal to use advanced imaging technology routinely as a primary screening method at transportation security checkpoints should be denied.

The proposal utterly fails to justify the costs against the infinitesimal incremental improvement in the ability of the TSA to detect a weapon that poses a significant threat to safe air travel. The proposal makes specious, unsubstantiated assertions, uses flawed reasoning, ignores certain costs, and misleadingly suggests that unrelated facts are somehow relevant to the alleged need for the AIT systems.


The TSA’s estimate of the net economic cost of the AIT systems are $2.4 billion over an eight year period, which includes the early trial period where costs were significantly lower. The run rate for just 2015 is $357 million.

By itself, this is a substantial incremental cost to justify. Certainly there are better ways to spend that kind of money that are less invasive and have a more substantial (and quantifiable!) net benefit. Consider the lives that could be saved by spending $357 million per year on roadway improvements in dangerous locations.

The TSA’s cost estimate is incomplete. The TSA screens approximately 1.8 million passengers per day or 660 million per year. The TSA analysis fails to compute the cost in lifetimes lost to the additional delay of AIT (and, as usual, they have provided no data to quantify this delay). If we conservatively assume that the security lines in airports are, on average, one minute longer with AIT than with traditional walk-through metal detectors (WTMD), that amounts to 18 lifetimes per year lost to waiting in line.

Also consider that many passengers are sole-proprieters, and thus “small entities” impacted by the rule change. Where has the TSA estimate the costs to them for time lost?

Non-Metallic Threats

The proposal argues that AIT is necessary because terrorists are focusing on non-metallic explosives, rendering the checkpoint WMTDs useless. They point to the shoe bomber, the underwear bomber, the alleged liquids plot, and to plots entirely outside of (and not targeted at) the United States. While it may be true that terrorists are considering non-metallic weapons, letting the TSA use AIT–even if AIT was 100% effective–wouldn’t have stopped any of these attempts, since none of them originated at airports where the TSA does screening.

Furthermore, the underwear bomb and the shoe bomb failed, in part, because it’s extremely difficult to detonate reliably a purely chemical explosive. Even the 1994 Bojinka Plot, which successfully detonated liquid explosives aboard an airliner headed for the U.S., relied on a detonater with metallic components that would have been detected with a modern WTMD. (It’s also interesting to note that today’s TSA rules wouldn’t even have stopped the bomber from bringing the liquid explosive through a checkpoint.)

Janet Napolitano was absolutely correct when she claimed success after the failure of the Umar Farouk Abdulmutallab to detonate his bomb. The rules in place before AIT are sufficient enough to drive would-be terrorists into desperate, risky schemes that involve unreliable devices. The plane landed with the suspect in custody an no injuries, except to Abdulmutallab. This is exactly what success looks like.


Let’s look at the effectiveness of AIT. Oh, that’s right. We can’t. The TSA either doesn’t know or won’t tell us the rates of false-positives and false-negatives. (Though John Pistole testified that the false-positive rate was higher than desired.) Without this data, it’s impossible to do a cost-benefit analysis.

If we look to other countries to get clues as to the effectiveness of AIT machines, we find that the German interior ministry has declined to roll them out because there are too many false positives to make them a useful screening tool. Italy found that the machines are too slow and ineffective.

My own experiences have indicated a tremendously high false-positive rate, causing lines to slow to the point that TSA agents allow some passengers to go through the WTMD instead simply to relieve the backup. (If the TSA proposal can rely on nothing but anecdotal evidence, then so can I.)

By replacing WTMD with AIT, the TSA is actually reducing its ability to reliably detect metallic weapons. They assert that any metallic anomaly on a person would be detected by AIT as reliably as by WTMD. This is false, as has been publicly demonstrated multiple times. Furthermore, a peer-reviewed article in a scientific journal explains how AIT scanning can fail to detect PETN explosives shaped to conform to the body. Perhaps this is why the Israeli airport security doesn’t think they’re useful.

If we examine the TSA Blog posts on prohibited items that have been found, we learn that virtually no prohibited items have been detected with AIT. Some of those finds (like the gun strapped to a passenger’s ankle) would have been found just as easily with a WTMD. Others, like small ceramic knives, might actually be allowed today as the TSA has wisely revised the guidelines about small knives.

Like many of the TSA’s rules, AIT makes the traveling public less safe in small ways. To submit to AIT or a patdown, the would-be passenger must remove virtually everything but they’re actual clothes. With a WTMD, you can keep your wallet (identification, cash, bank cards) and your boarding pass. With AIT, you cannot. Instead, the passenger must relinquish control and view of their most vital, hard-to-replace items. While the consequences of an individual lost wallet or boarding pass are small compared to explosives on airplanes, the AIT process greatly increases the rate of such losses while doing nothing to thwart the large-but-very-rare threats.

Until the TSA installs AIT on every security lane at every checkpoint in every terminal at every airport, it means that an observant terrorist with a non-metallic weapon can simply choose the WTMD line and avoid detection. Only the innocent are forced into the lose-lose proposition of AIT or patdown (often both). The proposal does not indicate if the costs of getting to the point where very lane has an AIT scanner are included in the eight-year cost projections.

Without real data as to the effectiveness of these devices, the TSA cannot possibly expect the traveling public to bear the invasiveness of the scanners and expect all tax payers to bear the tremendous cost of instituting this screening regime.


The TSA proposal asserts that there has been massive public approval of the body scanners, but they provide absolutely no data to back that assertion.

It seems, at nearly every airport, there is a checkpoint lane available that allows passengers to self-select for a WTMD instead of an AIT scanner. From observing the crowds at checkpoints, it’s very clear that the vast majority of people who recognize the opportunity to select the WTMD line will indeed choose that option over the AIT scanner. Every one of them should be considered an opt-out for AIT scanning.

The official way to opt out of AIT scanning is to submit to an invasive patdown. That’s a false choice. If TSA actually kept accurate tallies of opt-outs and opt-ins, the numbers would tell us nothing except whether passengers preferred one invasive form of search over the other. There’s no indication of how acceptable they find the concept of an invasive search overall.

Whether the opposition to AIT is a vocal minority, is irrelevant. The burden is on the TSA to demonstrate that AIT scanning is a cost effective, meaningful improvement to the screening process that remains within the bounds of theit mandate to perform minimally-invasive administrative searches for weapons.


No screening method will stop every threat. Every screening method has direct and indirect financial costs and some amount of unwanted invasion of privacy. When evaluating the addition of a new screening method to the mix or, as here, evaluating a replacement of one screening method (WTMD) with another (AIT scanning), we have to weigh the incremental costs against the incremental benefits. If the new screening method is approved, the terrorists will find a way past it. This arms race never ends. We’ll never get to 100% detection of weapons even with an infinite budget and limitless tolerance for invasive searches.

“Security at any cost” is impossible and a bad strategy. At some point, we have to draw a line and realize that additional spending and sacrifice of personal dignity won’t significantly improve the screening process.

The TSA, as usual, has not actually done a cost-benefit _analysis_. Instead, they’ve totaled up the bills and provided a vague, unconvincing argument that they must do something about non-metallic threats. They assert–without any supporting data whatsoever–that AIT is effective at detecting non-metallic items. This reasoning is faulty in so many ways that I find it hard to believe they can argue the point with straight faces. Clearly, as a nation, we’d be better off spending $357 million per year bringing logic and statistics courses back into the core curriculum of our education system.