Air travel can be stressful, even for experienced passengers. Between booking flights, organizing documents, and navigating busy airports, travelers have plenty to think about before boarding. However, some passengers encounter an unexpected detail on their boarding passes that can cause confusion: the letters “SSSS.”

The code stands for Secondary Security Screening Selection and is used by the Transportation Security Administration (TSA). When it appears on a boarding pass, it means the passenger has been selected for additional security checks before boarding the aircraft.

These checks can include detailed luggage inspections, electronic device testing, identity verification, and sometimes a physical pat-down. Passengers are rarely informed in advance, so the process can come as a surprise at the airport.

The selection is part of the Secure Flight program, which compares passenger information with government databases and security watchlists. The process is generally automated, and certain factors, such as last-minute bookings, one-way tickets, or mismatched personal information, may contribute to selection. In some cases, passengers are chosen randomly.

Importantly, receiving an SSSS code does not mean someone has committed a crime or is suspected of wrongdoing. It is simply an additional precaution intended to improve aviation security. Travelers who receive the code can make the experience easier by arriving early, keeping their belongings organized, and cooperating with security officers.