As millions of Americans pack their bags, package their gels and liquids into 3-oz. containers, and take off their shoes in preparation for holiday travel, transgender travelers will once again brace for encounters with Transportation Security Administration agents and an airport screening protocol that, advocates say, often singles out trans or gender-nonconforming passengers for heightened scrutiny.

The TSA has recently made efforts to address national outcry in the wake of trans woman Shadi Petosky’s viral tweets documenting her humiliating, problematic detention at Orlando International Airport in September — most notably announcing in The Advocate that agents will discontinue using the phrase “anomaly” to refer to perceived inconsistencies in a full-body scan. But the agency has a long history of institutionalized suspicion of gender-nonconformity.

Gender nonconformity, in the form of crossdressing, was identified as a possible terrorist tactic as early as 2003, by the then-newly minted Department of Homeland Security. In an advisory dated September 4, 2003, DHS warned that "terrorists will employ novel methods to artfully conceal suicide devices. Male bombers may dress as females in order to discourage scrutiny." The notice which contained this warning maintained the existing threat level at yellow (“significant risk of terrorist attack”), while noting that "recent terrorist incidents overseas highlight the possibility that Al-Qaeda could opt to conduct lower-scale attacks against 'softer' target sets," including VIPs who could be targeted by suicide bombers.

The threat in that advisory was worded so broadly, however, that transgender women in America who didn't dress in niqabs or burqas quietly had their bodies defined as terrorist bodies. And if "male bombers may dress as females in order to discourage scrutiny," then the counter to that is heightened scrutiny for those who don't conform to western societal sex and gender norms.

By early 2009, the September 2003 DHS advisory was identified as out-of-date, but changes that year to the air passenger screening process functionally institutionalized the premise of that advisory. Through new policies outlined in a program called Secure Flight, DHS reinforced gender norms, requiring that a passenger’s gender marker on their official identification match that listed on the ticket purchased.

"Secure Flight is a program developed by the Department of Homeland Security (DHS) in response to a key 9/11 Commission recommendation," the Transportation Security Administration posted on its Secure Flight Program Web page that year. This was ostensively done to provide "uniform watch list matching by TSA."

Basically, Secure Flight added gender to the passenger screening process in 2009. That year began the requirement that gender markers on identification cards had to match the gender declared when buying an airline ticket. "By adding date of birth and gender," the TSA wrote on the June 4, 2009 iteration of the Secure Flight webpage, "the number of misidentifications is reduced further and can more readily identify passengers who do not pose a threat."

The indirect implication is that gender expression should conform to Western societal gender standards, with the corollary concept that gender expression that doesn't match those norms must be inherently suspicious.

This might seem like a reasonable expectation — that one’s legal identity should be reflected on a boarding pass. But transgender people's gender markers on their state identification cards don't always match their expressed gender. Without costly, involved genital surgeries that are often beyond many transgender people's economic reach — and often unwanted because these are so invasive — many can't change the gender markers on their IDs.

In an apparent effort to address the gender marker issue on official ID forms, the Department of State changed how it handles gender changes on passports in June 2010. Under the changed rules, a transgender person can obtain a passport that matches their gender identity without invasive surgeries that many people choose to forgo. This change at the State Department took a step toward addressing TSA’s Secure Flight guidelines that require gender markers to match on state-issued ID and on the purchased ticket.

But gender markers don't address bodies.

On Christmas Day, 2009, a man known to us all now as the Underwear Bomber boarded a flight from Amsterdam to Detroit, Mich. His subterfuge officially designated as a legitimate security concern the question of what’s between the legs of all U.S. air travelers.

Electronic scanning procedures already surveyed the intimate areas of air travelers, but the Underwear Bomber placed an additional, intense focus on passengers' genitalia. In February 2010, full-body imaging scanners began arriving at U.S. airports. By November 2010, there were, according to the TSA, 400 full-body scanning machines at 69 airports nationwide. Currently, all U.S. airports that have had more than 250,000 boardings annually for the past three consecutive years use full-body imaging scanners, according to Airport Improvement Magazine.

Initially, the full-body imaging scanners showed an air traveler's full anatomy to a TSA agent who never saw or met the actual passengers. If one didn't wish to be electronically scanned and have their "junk" visible to a TSA agent, then the alternative was an aggressive pat down.

As anatomically specific scanning didn't sit well with many in the American public, less intrusive scanner software was introduced. The newer scanner software is gender normative in that it reads bodies according to two categories: male and female. TSA agents now literally select the pink or red button for a female passenger, and the blue button for a male passenger. As a TSA official told The Advocate in October, agents are trained to select a gendered scanning option based on how they perceive the passenger’s gender presentation.

So, what fixed a privacy concern for the majority of the public opened up a can of worms for transgender passengers, or anyone who has a body or gender expression that doesn’t adhere to the strictly binary guidelines defined by American culture.

What’s more, security screening that includes using full body scanners isn't proving effective. ABC News reported in June that an internal investigation by the TSA found that 95 percent of the time — in 67 of 70 cases — TSA "red teams" (controlled agents testing the screening program’s efficacy) were able to get potential weapons through TSA checkpoints.

In addition to the body-scanners, TSA uses what it dubs the Screening of Passengers by Observation Techniques, also known as the SPOT program. A report provided to Nature in 2010 called into question the effectiveness of SPOT criteria that aims to identify suspicious, anomalous behavior, especially since there was a lack of peer review of that criteria. And in 2013, the U.S. Office of the Inspector General criticized the program, stating:

“TSA has not implemented a strategic plan to ensure the program’s success. For example, TSA did not (1) assess the effectiveness of the Screening of Passengers by Observation Techniques program, (2) have a comprehensive training program, (3) ensure outreach to its partners, or (4) have a financial plan. As a result, TSA cannot ensure that passengers at United States airports are screened objectively, show that the program is cost-effective, or reasonably justify the program’s expansion. In fiscal year 2012, TSA’s Behavior Detection and Analysis Division developed a draft strategic plan that includes a statement of mission, goals, and objectives. However, the plan had not been approved and implemented at the time of our review.”

In March of this year, Intercept obtained a confidential TSA document that identified the 92 criteria specially trained TSA agents, known as Behavioral Detection Officers, use in the SPOT program. That document, referred to as the SPOT Referral Report, has a section called "Deception Factors" which includes suggestion that BDOs pull aside for additional screening anyone who “appears to be in disguise.” In a separate section labeled “Signs of Deception,” agents are instructed to be aware of any “change in voice, pitch, rate, volume, choice of words, dry mouth” that passengers display while undergoing screening. That same section also identifies an “Adam’s apple jump,” a face becoming flushed, and “trembling of voice and body” as indicators of suspicious persons. If a passenger “displays two or more” of these “signs of deception,” BDOs are required to notify a law enforcement officer.

Under another section called "Fear Factors," line items warranting additional scrutiny include a passenger’s "Exaggerated emotions or inappropriate behaviors to the location such as crying, excessive laughter, or chatter," "Hesitation/indecision on entering checkpoint or submitting to screening process," "Scans area, seeming to look for security personnel or [Law Enforcement Officer]," "Shows unusual interest in security officers and their work routines," or "wearing improper attire for location."

It’s not hard to imagine how these broad categorizations of “suspicious behavior” could just as easily be the characteristics of a trans person nervous about being outed by a uniformed government official in a public space. According to the SPOT program, being perceived as a “man in a dress” while at an airport continues to be a reason to be subjected to heightened security screening.

While trans people and other gender-nonconforming individuals are the most directly impacted by these sweeping “precautions,” they are by no means the only group of travelers singled out. Some members of the disabled community are subject to heightened scrutiny due to use of prosthetics, such as breast forms, hairpieces, and artificial limbs. In fact, many transgender people who aren't disabled use prosthetics as well, including breast forms, binders, and hairpieces — so transgender people who use prosthetics are doubly “suspicious.”

So while the September 2003 DHS advisory which stated "male bombers may dress as females in order to discourage scrutiny" may no longer be in effect, everything about that advisory's statement is functionally still in effect, and then some. It’s also worth noting that there have been few, if any, verified reports of male terrorists in the U.S. or abroad seeking to disguise themselves as women to avoid scrutiny.

The message these policies send to the American public is clear: Those who don’t conform to strict, binary gender presentation are to be treated with suspicion. When it comes to airline security, anyone who exhibits behavior deemed non-normative or “inappropriate,” according to an agent’s assessment, is a possible security risk. Although it may not be intentional, this system implicitly institutionalizes the assumption that transgender bodies are terrorist bodies, and that trans people are inherently threatening. When transgender passengers voice concern about the heightened security screening measures, they are likely to be flagged as even more suspicious.

But here’s the kicker: transgender people have actually shown themselves more likely to be security assets to the U.S. than the general public. Specifically, transgender people are twice as likely to have served in the military as the general public: 21 percent of trans people have served in the armed forces, compared to 10 percent of the cisgender population. The Department of Defense has now stopped discharging transgender service members just for being transgender, and appears close to announcing a policy that permanently allows open transgender military service.

Finally, it bears mentioning that there’s also been no reported case of a transgender terrorist since that September 2003 DHS advisory.

AUTUMN SANDEEN retired from the U.S. Navy in 2000 with 20 years of service. In 2010, she and other LGBT veterans were jailed twice in direct actions at the White House advocating repeal of "don't ask, don't tell." In the past she blogged for Pam's House Blend, and currently she is an editor at Transadvocate and a columnist for LGBT Weekly.