If you have trouble checking in for your next flight online, that mean that you were tagged with the four letters that no traveler wants to see. The dreaded “SSSS” on your boarding pass.
The “SSSS” label stands for “Secondary Security Screening Selection”, and was instituted by the Transportation Security Administration (TSA) right after the September 11th attacks in 2001. This additional layer of security helps to prevent people of interest from boarding commercial aircraft.

If you do find yourself marked with the “SSSS” label, here is what you can expect.

– Additional identification verification upon checking in for the flight
– Inspecting all travel documents
– Additional questions / scrutiny with Customs and Border Protection agents
– Mandatory pat-down inspection in security
– Luggage hand searched and swabbed to check for explosive residue