Remember the last time you went through airport security? You probably wondered what those TSA agents could actually see. Most of us follow instructions—stand here, arms up, hold still—without knowing what information those scanners collect. The truth might surprise you. Let’s look at what these machines detect and what they mean for your next trip.
The technology behind airport scanners
Most airport body scanners use millimeter wave technology. These machines bounce radio waves off your body to create an image of what’s underneath your clothing. They detect items hidden between your body and clothes by measuring how waves bounce back. This lets security spot things metal detectors would miss, like plastic explosives or ceramic knives.
When first introduced, these scanners created detailed outlines of your naked body. After public outcry, the technology was updated. Now, instead of showing your actual body, machines display a generic avatar—the same outline for everyone.
What many travelers don’t realize is how sensitive these scanners are. They detect things as small as a piece of paper or perspiration. That’s why you might get flagged for a pat-down even when you’re sure you don’t have anything on you. The machines might pick up wrinkles in clothing, a forgotten tissue, or the outline of underwear with metal components.
The newest scanners are becoming more sophisticated. Some airports test systems that scan you while walking normally. Others develop technology letting you keep shoes on. These advances might make security faster, but they also mean scanning becomes more thorough and less obvious about what information it collects.
What security agents actually see
Modern scanners display a generic, gender-neutral outline—like a simple mannequin. The system highlights unusual areas with a yellow box. This could be anything from a forgotten phone to a belt buckle. Agents don’t see your actual body shape, skin, or anatomical details.
This differs greatly from early scanners that showed detailed images revealing body contours. Public backlash was immediate. People worried about privacy violations and potential image sharing. These concerns led to major changes in how the technology works.
You can actually see the same image the TSA agent sees. The scanner usually has two screens—one facing the agent and one facing you. This transparency specifically addresses privacy worries. Next time you’re at the airport, watch your own scan appear with the same yellow boxes on both displays.
Using artificial intelligence, newer systems can often distinguish between harmless items and potential threats. This reduces false alarms and unnecessary pat-downs. However, the system makes judgment calls based on shape, density, and location. These judgments aren’t always perfect, which explains why you might get flagged while carrying only everyday items.
Surprising items that trigger alarms
Numerous everyday items trigger those yellow boxes. Thick hair—especially buns, braids, or dreadlocks—frequently causes alarms because dense hair blocks scanner waves. Many Black travelers report being singled out for additional hair searches because of this limitation.
Body jewelry is another common trigger. Belly button rings, nipple piercings, and other body modifications often result in secondary screening. Underwire bras can be particularly problematic—the metal supports trigger alarms so frequently that many travelers pack wire-free bras for flying. Even perspiration can create anomalies, as water affects how radio waves reflect.
Medical devices often lead to scanner alerts too. Insulin pumps, ostomy bags, knee braces, and certain bandages can trigger the system. Some travelers with artificial joints report always being pulled aside despite carrying medical documentation. The machines also flag clothing with reflective material, sequins, or metallic threads that affect scanner readings.
Even more surprising are everyday items that cause problems: tissues in pockets, gum wrappers, clothing tag stickers, laundry detergent residue, and paper money with security features. Those little silica gel packets from shoe boxes? If one gets stuck in a pocket seam, it might look suspicious enough for additional screening.
What scanners can and can’t see inside your body
One big misconception: airport body scanners can’t see inside your body. Millimeter wave technology only detects objects between your body and clothing. The waves bounce off your skin rather than penetrating it. They won’t reveal internal medical devices, implants, or objects inside body cavities. Tampons, IUDs, and pacemakers won’t show up.
This limitation has security implications. People smuggling items internally won’t be detected by standard scanners. That’s why airports with heightened security sometimes use additional methods like behavioral analysis or drug-sniffing dogs. The scanners primarily find weapons and explosives that threaten flight safety.
While scanners can’t see inside you, they’re extremely sensitive to what’s on your skin surface. Medical patches, certain body paints, and even some tattoo inks (particularly older ones with metal-based pigments) can be detected. This sensitivity explains why some travelers with extensive tattoo work report more frequent additional screening.
How scanning technology has evolved
Airport security scanning has changed dramatically since the early 2000s. Initial machines used backscatter X-ray technology, which projected low-level X-rays onto passengers, creating detailed images of bodies beneath clothing. Security agents could see outlines of genitalia, breast implants, and medical devices.
By 2013, most airports switched to millimeter wave technology with automated target recognition software. This eliminated detailed body images, replacing them with generic avatars. When objects are detected, they appear as yellow boxes rather than showing the actual item against the passenger’s body.
The most recent evolution involves artificial intelligence and machine learning. Modern scanners better distinguish between ordinary items and potential threats. Some airports have tested machines allowing passengers to keep hands at their sides rather than raising them overhead, making the process more comfortable and accessible.
Looking ahead, the Department of Homeland Security is developing “Real-Time AIT” panels that can screen passengers as they walk normally through checkpoints. They’re also working on shoe scanners that would let travelers keep footwear on, making security both more thorough and less intrusive.
Your privacy rights at security checkpoints
Many travelers don’t realize they have options at airport security. You have the legal right to refuse body scanning completely. If you’re uncomfortable with the technology for any reason, you can request an alternative screening method. TSA agents must honor this request, though they might not volunteer this information.
The alternative is a physical pat-down, typically conducted by a TSA agent of the same gender as you present. You can request this pat-down be performed in a private room with a witness present. While some find pat-downs more invasive, others prefer human interaction to machine analysis.
For travelers with medical devices, religious headwear, or special circumstances, additional rights apply. You can inform agents about your situation before screening begins. Those with medical implants can request pat-downs avoiding sensitive areas. People wearing religious head coverings can request to pat down their own headwear, then have their hands tested for explosive residue.
Exercising these rights might require additional time. Some travelers report more thorough pat-downs when opting out of scanners. However, TSA isn’t permitted to single you out for additional scrutiny solely because you’ve exercised your opt-out right. You can ask to speak with a supervisor if you feel unfairly treated.
Scanning variations worldwide
Airport security scanning varies dramatically by country. The United States has rigorous, technology-intensive screening with body scanners at virtually all major airports. European countries often take a more selective approach, using scanners for secondary screening rather than every passenger. Many European nations employ more human-based methods, relying on trained officers alongside technological screening.
Asian countries present another approach. Japan features efficient, courteous screening processes with newer technology. Security staff often bow after screening is complete. China has implemented comprehensive security systems, including facial recognition technology integrated with body scanning.
Middle Eastern hubs like Dubai and Abu Dhabi balance security with passenger comfort. Their scanners are housed in aesthetically pleasing surroundings with privacy considerations built into checkpoint design. Female travelers in traditional dress may use separate screening areas with female officers.
Israel’s Ben Gurion Airport relies less on universal body scanning and more on sophisticated profiling and interview techniques. Passengers are questioned by trained security personnel before physical screening. These questions identify behavioral anomalies that technology might miss, creating a multi-layered approach beyond what scanners alone detect.
Next time you’re standing in a scanner with raised arms, remember you’re experiencing just the current phase in evolving security technology. While today’s technology might seem invasive, it’s actually much more privacy-conscious than early systems. Future scanning might become so seamless you barely notice it happening. The challenge continues to be finding the right balance between thorough screening, passenger privacy, and efficient security lines.
