Having just returned from another air trip, I relate the following story.
On this trip, a one day in and out to a southern city, I carried in my rolling card a video projector, which we use for our pitch presentation to Potential Client.
Also on my person is a home-made burrito (I bring food on my trips, because I can't ever find healthy choices when I travel), and in rolling bag, in a pouch, is, as there has been for over a year, a small folding knife:
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The knife was accidentally left in a pouch and it was my intention to remove it long ago, but the knife has been to Chicago with me so many times, that I decided to just leave it in there.
Well, my bag has been hand-checked several times (the burrito always gets attention) and it's been about a year now and not once have they picked up on this knife. I have a mailer, ready to go, but the knife just sits there.
I feel safer.