This topic has been discussed at great lengths.
Experiences vary greatly from folks who've been turned away because of fingernail clippers to people who have waltzed aboard with broadswords hanging off their belts.
A lot of people like to quote "The Rules." But, the bottom line is this: it doesn't matter how long your blade is, if it's serrated or not, fixed or folding, locking or not, black or mirror-polished... if the $7.50/hour "guard" does not like the looks of you or your knife, you and your knife will not get aboard. The "rules" are really just guidelines because, in the end, the "guards" have total discretion.
I have taken upwards of a hundred domestic flights carrying my AFCK and picked people up at airport gates countless times more. I have never been stopped, only questioned a couple of times, the knife is hardly ever examined. I don't burry it in my bagage, and I don't try to hide it or disquise it. I just drop it in the change tray along with my pen, my keys, my watch, my Leatherman PST, and whatever other metal I might have on me, hand the tray to the "guard" and pick it up on the other side.
The technique that has successfully got me and my AFCK through airport security at dozens of airports nationwide with no complications is what I call "innocence by association." If you dress like a gentleman, act like a gentleman, and speak like a gentleman, then your AFCK is, by association, just a harmless gentleman's pocket knife.
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Chuck
Balisongs -- because it don't mean a thing if it ain't got that swing!
http://www.balisongcollector.com