(CNN) A self-described "professional traveler," Kristin Beck knows the airport security drill.
On Tuesday afternoon, the retired transgender Navy SEAL was bound for Kansas City to give a speech to federal employees about gender sensitivity. It's what she does, ever since she stopped going by her birth name, Christopher Beck, and wrote a book about her life as a member of SEAL Team 6. She was featured in the CNN series, "Lady Valor."
She arrived at Reagan National Airport with enough time to spare, but not too much. Beck told CNN she entered the security checkpoint, put her bags on the conveyor belt and stepped into the body scanner, as she's done countless times before.
When flagged for secondary screening, she took it in stride. She said she waited for one of two Transportation Security Administration agents -- a man and a woman -- to step forward and pat her down. Instead, they turned their backs to her and started whispering.
But to Beck, it was clear what was happening. Despite her makeup, long hair and low-cut blouse, the agents thought she was a man. It wouldn't be the first time since she began publicly living as a woman.
But it still was humiliating, Beck said. It never gets easier.
"I'm a female," she said she told them. "It's no big deal."
Apparently, it was enough to prompt the the agents to call their supervisor, she said. When he arrived, the supervisor directed the male agent to pat "him" down in front of the security line, as everyone waited.
"These are my real boobs, he's not going to pat me down," she recalls telling agents.
"This is wrong. I'm a female, it says female on my Maryland driver's license. This is the real me."
According to Beck, the supervisor responded, "Then somebody pat him down."
Ultimately, female agent did the pat-down, Beck says. After that, Beck went on her way, holding back tears. She pulled out her phone and recounted the experience in a Facebook post.
"I'm sad, for TSA, our country, our future ... Why is this so difficult?" she wrote. She noted the irony of her destination, to a conference where she would give a speech to federal employees on human rights.
According to TSA guidelines, when passengers go through a full body scanner, the TSA agent selects a button indicating man or woman, depending on how the person looks. The equipment conducts a scan and alerts areas of the body warranting further inspection, which is often the case when a person's anatomy is inconsistent with the body type selected.
From there, the officer is trained to clear the alarm and conduct additional screening to determine whether a prohibited item is present, the guidelines say.
A TSA spokesman said the agency has reached out to Beck to make things right.
TSA employees receive cultural awareness and sensitivity trainings, through webinars and in-person sessions, focused on engaging and screening transgender passengers. New training modules are being developed with feedback from transgender advocacy groups.
"We regret that Ms. Beck had a negative screening experience and apologize for any embarrassment or discomfort this experience might have caused. We have contacted Ms. Beck to discuss her concerns and will continue to work with her and other members of the transgender community to improve training and protocols," said spokesman Bruce Anderson.
"We are committed to ensuring that all travelers are treated with respect and courtesy. We continue to supplement standard operating procedures with training aimed at providing our officers with the tools they need to ensure they are sensitive to the needs of travelers and engage positively and appropriately with transgender passengers."
Beck shared the incident the next day in her speech. Afterward, she said TSA employees came up to her and apologized. Not all employees are like that, they told her.
She believes it. She says she knows people who work for the TSA. Some of them saw her post and shared it with their leadership, who contacted Beck about the incident, she said.
She's glad it happened to her, a mature combat veteran who has steeled herself against the trials of being transgender, instead of someone vulnerable, someone who's starting their journey.
Beck hopes it becomes a teachable moment, a prompt for more training and education.
"The TSA does a great job 99% of the time. This is a 1% error," she said. "They have a tough job but they need to continue training and continue to do better."