A pocket knife is a rather absurd weapon anyways to anyone with common sense. Sure it could be used as a weapon, but it's not something that would keep passengers from stopping a terrorist in 2013. I don't know if pocket knives were technically allowed or just overlooked because of the above reason. My reference was in regards to the obvious (guns, swords, explosives, etc). I was at Sky Harbor Airport in Phoenix in the late 90s and the entire airport was shut down when someone went through security with a gun.
Pedantics aside, airport security used to have common sense. Now, it's been tossed out the window for zero tolerance "no need to think" policy. It doesn't mean we should return exactly to the laws of the 1990s for airport security in the US, but the "security theater" for the sake of making people think they're safer by inconveniencing at best and harassment/theft/groping at worse is ridiculous.
That would all depend on the model in question[1]. 2-3" blade is pocket knife size. If going by wiki[2], it defines pocket knife as 2-6". 6" is pretty big for a what one would define as a pocket knife though.
Pedantics aside, airport security used to have common sense. Now, it's been tossed out the window for zero tolerance "no need to think" policy. It doesn't mean we should return exactly to the laws of the 1990s for airport security in the US, but the "security theater" for the sake of making people think they're safer by inconveniencing at best and harassment/theft/groping at worse is ridiculous.