What ‘SSSS’ means if you see it on your airplane ticket

What It Means When There's An 'SSSS' On Your Boarding Pass

Most of us probably don’t know what any of those codes mean on your boarding pass, but there’s one that you won’t want to see when you’re flying. It’s a simple series of repeated letters, SSSS, and it means that you’ll be subject to additional screenings.

The SSSS is an acronym for Secondary Security Screening Selection. You and your luggage will be subject to a closer screening. You will be patted down, swabbed for explosive residue and your luggage will be opened and searched, News.com.au reported.

You may have to provide extra information to prove who you are and give complete travel plans in detail to screeners.

SSSS was developed by the Transportation Security Administration after 9/11 to prevent those who shouldn’t get into the U.S. from traveling here.

"Secure Flight is a risk-based passenger prescreening program that enhances security by identifying low and high-risk passengers before they arrive at the airport by matching their names against trusted traveler lists and watchlists," TSA officials told Business Insider.

The list that feeds the SSSS code is a secret. The TSA said that people are added to it after a computer randomly selects travelers.

One clue that could mean that you may be on the list is if you can't use online check-in for a flight, News.com.au reported.