Originally Posted by
GUWonder
For most circumstances of the sort akin to that of the OP, the airline's security contractor do this thing. And it mostly has nothing to do with having been to "countries with questionable relations with the US".
Book a trip for a friend or give someone an upgrade lately? Happened to me after I let a friend use an upgrade sticker for a couple longhaul international flights.Turns out, the friend required going through redress process. Until he did, I kept getting the dreaded "SSSSS" by affiliation. The day after his redress process ended, I flew into the US and the "SSSSS" was gone. Haven't seen it since.