I came back from a trip to South Florida a couple weeks ago where I just got certified and bought new equipment. I checked everything but my computer and regs, which I had in a padded reg case. I got through security without any problems. Its a good thing because I forgot to pack my hose mounted titanium dive knife in my checked baggage. It was on my LP BC hose in my carry-on. I remembered it was there about halfway back to MN. I am glad they did not find it, I probably would have lost it. But it kinda makes you wonder how the TSA could miss a 4" knife. Since that trip, I moved the knife mount to the corrugated hose directly on my BC. That way it is always checked and I can't forget it, and chance bringing it on the plane with me again. Oops
Which brings me to my point: Always remember to pack your dive knife with your checked luggage.