A boarding pass contains important information about an upcoming flight. Seeing TSA PreCheck on a boarding pass brings joy to a traveler's face because it means they get to use the expedited security lanes.

However, a different set of letters can ruin a traveler's day: "SSSS" indicates that you've been selected for secondary screening before boarding your flight.

Here's what SSSS on a boarding pass means, why travelers get it, and how to reduce being picked for secondary screening in the future.

What does SSSS mean on a boarding pass?

A Secondary Security Screening Selection or SSSS designation on your boarding pass means that you’ve been picked for a secondary security screening.

The Transportation Security Administration (TSA) may select passengers for SSSS on flights from, to and within the U.S.

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Why do travelers get SSSS?

TSA doesn’t publish specific guidelines on why certain passengers get SSSS markings on their boarding passes.

Anecdotally, passengers with unusual travel patterns, one-way international flights and travelers to certain countries get it the most. It is also possible that TSA assigns SSSS markings randomly.

Warning signs that you may have been selected for secondary screening

If you’re selected for secondary screening, you’ll find out when you print out your boarding pass. Your fears will be confirmed when you see the bold “SSSS” letters on your ticket.

However, some signals suggest you may have been selected for your next flight.

Can’t check in online or through a mobile app. Many travelers use an airline's website or mobile app to check in and obtain boarding passes. While technology can break, not being able to check in is a sign that an SSSS designation is in your future.

Trouble using airport kiosks. Kiosks expedite check-in at the airport without having to speak with anyone. If you can’t check in to your flight or receive a message asking to speak with an agent, you may have been selected.

You are directed to check in with an agent at the airport. The airline may send you a note via email, text or its mobile app directing you to speak with an agent at the airport.

What happens if you have a boarding pass with SSSS on it?

Travelers selected for secondary screening typically have to go through one or more extra security screenings before they can board their flight.

These extra security inspections can include the following:

Go through a metal detector. Walk through a metal detector for airport security to verify that you aren't carrying weapons or other dangerous objects.

Receive a pat-down. This manual inspection detects objects that a metal detector may miss.

Additional bag inspection. All belongings in your personal item (such as a backpack or purse) and carry-on luggage must be removed from your bag for inspection. They may also thoroughly inspect the bag, including its pockets and zippered lining.

Test for explosives. They may swab you and your luggage for explosive residue.

The timing for this process varies based on how in-depth the search is and which of the above methods that security uses for its screening.

My experience getting SSSS on my boarding pass

I take dozens of flights every year, and I’ve been selected for secondary screening only once.

My son and I were traveling back from Denmark on a one-way Air France Business Class award ticket in 2019. I noticed the markings when my boarding pass was printed out, but I didn’t think much of it.

I was asked to step into an enclosed area when our flight started boarding. Since my son was a minor, they allowed him to come into the room with me.

The security person was friendly, but all business. He asked me to remove everything from my backpack and carry-on luggage on the table so he could inspect them. After a few minutes, they cleared me and allowed me to repack my belongings. Then, we left the room and were allowed to board.

It was a little scary since I didn’t know why I was picked. But the process was efficient and quick, and we didn’t miss our flight.

How can you reduce SSSS markings in the future?

If you keep getting the dreaded SSSS on your boarding passes, try these strategies to make travel easier in the future.

Apply for TRIP

Travelers who receive multiple SSSS markings should consider applying for the DHS Traveler Redress Inquiry Program (TRIP). You can submit your application online or on your phone in minutes.

Travelers who submit a DHS TRIP Traveler Inquiry Form are automatically assigned a unique seven-digit identifier. You'll include that Redress Control Number when booking flights, allowing TSA to review your profile beforehand.

Book round-trip flights

Some travelers say that booking one-way flights increases the odds of being picked for secondary screening.

While the miles and points community often use one-way flights to take advantage of pricing and award availability, this behavior can seem suspicious to TSA.

Avoid traveling to certain countries

Certain countries are considered higher risk to TSA and the Department of Homeland Security.

Even if you're traveling to see family or as a tourist, your profile could be deemed higher risk. Consider having family visit you or pick different countries to reduce your chances of secondary screening.

The bottom line

While travelers may be concerned when SSSS is printed on their boarding passes, it isn't as bad as you fear.

Something about your trip may have triggered concern with TSA, so they need to perform a secondary screening of you and your bags. This process usually takes a few minutes, but it could take much longer.

In some cases, you may miss your flight or be one of the last to board the plane. If you get SSSS on your boarding pass regularly, consider applying for a Redress Control Number, which may reduce the inconvenience.