Air travel is designed to move millions of people quickly and efficiently, but for some passengers, the journey includes an unexpected delay marked by four letters on their boarding pass: SSSS. SSSS stands for Secondary Security Screening Selection, a designation used by the Transportation Security Administration (TSA) to indicate that a traveler has been selected for additional screening. Spotting this code—usually printed near the gate or seat number—means the airport experience will be more detailed and time-consuming than usual.

The SSSS designation is part of the U.S. government’s Secure Flight program, a pre-screening system that reviews passenger information provided during booking, including name, date of birth, and gender. This data is checked against government watchlists to identify potential risks and prevent mistaken identity. Importantly, most travelers flagged with SSSS have done nothing wrong. In many cases, passengers are chosen randomly to maintain unpredictability in airport security.

Travelers with SSSS are typically unable to check in online or at self-service kiosks and must receive their boarding pass from an airline agent. At the security checkpoint, they are directed to secondary screening, which may include a thorough inspection of carry-on bags, explosive residue testing, device checks, and a detailed pat-down. The process can add 15 to 45 minutes to security time.

The best advice for passengers selected for SSSS is to remain calm and cooperative. Arriving early, keeping documents accessible, and ensuring electronics are charged can help reduce delays. While inconvenient, SSSS is considered a routine part of modern aviation security, designed to enhance safety across the global air travel system.