Last time I checked in with a fire arm, they made me take it out of the locked and cabled metal case inside my luggage (don’t want TSA to have an easy time stealing it), open the action and show that it was not loaded. I was weird to do that with everyone in line watching suspiciously. Yikes.
They then put a red tag on my bag saying there was a gun inside. BUT the counter guy at the last second tucked the tag inside my luggage and closed it. He said that he had to put the tag on the luggage but said that regulations did not say it had to be visible. Cool.
I flew shortly after 9/11 and carried. The agent at the counter asked me to do the same (demonstrate that the weapon was cleared). I quietly asked “Right here?!” and she nodded yes. I cleared my weapon as discretely as I could and then locked it in the case, and returned the case to my suitcase.
They put a conspicuous red tag that just screamed, “Steal Me!” on the suitcase. I had anticipated this and pulled a small roll of duct tape from my pocket, wrapped the suitcase a couple of times, and then autographed it with a Sharpie right at the seam for the lid.
I was actually surprised when I saw it at the other end of my trip.
I also put my "WepCase" on the counter, unlocked, and with the slides locked open on my semis -- and offer to open the case for their inspection.
Most agents appreciate your making it a routine transaction for them.
(The airlines long ago learned that external tags were invitations to theft -- and, for years, have routinely put the [filled-out and signed] declaration tags inside the case before you lock it...)