The Transportation Security Administration (TSA) employs a random and layered security measure known as "Secondary Security Screening Selection" or "SSSS." This additional screening is part of the TSA's Secure Flight program, which uses passengers' personal information to distinguish between high-risk and low-risk travelers. According to the TSA, "movements of large amounts of cash through the checkpoint may be investigated by law enforcement authorities if criminal activity is suspected."
Passengers marked for SSSS undergo further checks based on various factors, including travel history or itinerary anomalies such as one-way tickets or using multiple passports. The Department of Homeland Security (DHS) supports this process with data from agencies like Customs and Border Protection (CBP), Immigration and Customs Enforcement (ICE), and others.
Some passengers experience repeated SSSS screenings due to their names resembling those on the No-Fly List. To resolve such issues, travelers can apply for the DHS Traveler Redress Inquiry Program (TRIP). Upon approval, a redress control number is provided to help avoid future SSSS designations.