SSSS can occur at strange times: I was flying lga-stl-las, my boarding passes for the entire trip had NO SSSS's when I printed them in lga; I stopped into the aa lounge on my arrival in stl and found that my upgrade from stl-las had cleared, but the bp for that leg was SSSS'd (even though I was intransit) the agent was able to print a new bp without SSSS--but on my return trip my bp had an SSSS.