So it seems that my initial question has been answered. US (or even foreign) government clearances don't have any part of either picking or not being picked for an SSSS interrogation.

I guess it just worked out for me that in any situation and performing certain (last minute, first class fares) transactions won't ever signal me for an SSSS.

So, the obvious next question: Does anyone have the process figured out on who is selected and how that determination comes in? If it really is purely up to the airline, are they mandated at all by any federal agency? Otherwise, what's to say that Airline A picks an allotment of 10% of passengers that pose no specific threat, while Airline B picks the same 10%, although all are suspected 'risky' passengers...and Airline A decided to pick its 10 based on non-FFs, non-high revenue, last minute purchases? Do the airlines get audited every so often?

-jeremy