'SSSS'. It's a seemingly random set of letters on the boarding pass for your domestic US flight, but it means you're in for an extra security screening by the TSA agents.
The letters themselves stand for Secondary Security Screening Selection, although neither the TSA nor the airlines have revealed the criteria on which passengers are chosen.
So what does it mean when you see those letters appear on your boarding pass?
As well as the typical baggage x-ray and walk through metal detector (or body scanner), you could be in for a pat down, a manual baggage search, explosive trace detection or a once-over with a hand held metal detector – or even all of the above.
For this reason, if you notice upon checking in for your flight that your boarding pass is adorned with 'SSSS', we suggest heading directly to the security checkpoint because your screening time will take longer than usual.
Once you've been through those extra checks and have been cleared, a TSA officer will apply some distinctive markings to your boarding pass – in the photograph shown, this is the handwritten 'SSSS-10' and the three stars next to 'SSSS', although the markings change frequently and vary from airport to airport.
Those annotations on your boarding pass indicate that you’ve been screened appropriately to airline staff at the boarding gate.
It's a good idea to make sure that these annotations have been made once you're finished with the additional checks – if your boarding pass lacks them, you won’t be able to board until you've been re-screened.
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