HOUSTON - Worldwide human trafficking is a $150 billion industry annually.

Houston comes in as one of the worst cities in the United States for human trafficking. It happens in plain sight but still goes unnoticed.

Often times, transportation officials are considered the first responders because that’s where trafficking often takes place. On Tuesday, Airline Ambassadors International, a non-profit, held an event at Bush Intercontinental Airport, training airline staff and law enforcement on what to look for.

Red flags include children traveling without bags, being poorly dressed compared to the adult they’re with and women and children not being allowed to answer questions for themselves. It’s important to know that men are trafficked too, often times for labor.

It’s believed there are currently 20 millon victims of human trafficking around the world and that every year, more than 2 million women and children are sold into slavery.

Anyone who would like to report suspicious human trafficking activity can contact Airline Ambassadors international, ICE or the Department of Homeland Security.