Alarm bells went off for flight attendant Shelia Fedrick when she saw a girl with greasy blond hair sitting next to an older well-dressed man.

Fedrick told NBC the girl "looked like she had been through pure hell."

So Fedrick approached the individuals and tried to make conversation. The girl would not look at her or make eye contact, according to 10 News. The man answered for her and became defensive. "Something in the back of my mind said something is not right," Fedrick said.

Fedrick told the girl under her breath to go to the bathroom, she said.

"I left a note in one of the bathrooms," Fedrick told NBC News. "She wrote back on the note and said 'I need help.'"

Fedrick told the airline pilot about the situation, and when they landed in San Francisco, California, the police were there waiting for them.

Since the 2011 incident, Fedrick and the girl still keep in touch today. She now attends college, the Metro reports.

The change one person can make

It is stories like these that led Nancy Rivard, founder of Airline Ambassadors, to teach airline staff how to recognize and report human trafficking. Fedrick shared this experience from 2011 to 100 flight attendants who gathered in Houston, Texas for a two-day seminar.

At the seminar led by Rivard, they were taught to look for ashamed, bruised, drugged or frightened passengers who are traveling with someone who doesn't look like their parent or relative. Other signs include someone speaking for another individual, not letting them out of their sight or becoming defensive, NBC News reports.

Rivard has been educating flight attendants about human trafficking since 2009, according to NBC News, and she continues to travel across the country to teach.

"[Flight attendants] are a great tool in the fight against human trafficking, as spending hours on a plane, they have a unique opportunity to see how someone behaves," The Wingletreports.

Fedrick changed the life of one woman that day on the plane, but she's also changed countless other lives from participating in Rivard's trainings.

Take action

One person really can make a difference.

In 2016 2,000 human traffickers were arrested and 400 victims found, according to NBC News.

Here's how you can help:

If you suspect that you see a victim of human trafficking, take a photo and send it to 909-ALERT-US (909-253-7887) or call the Human Trafficking Hotline at 1-888-373-7888.