I wonder how many "incidents" have occurred with checked firearms while the firearm is in the possession of the airlines?

Just how many times have passengers either jumped onto the tarmanac and grabbed firearms from a locked case and caused an incident, or crawled down intoi the luggage hold and obtained a checked firearm and caused issues?

My question is what is the actual risk(s)these procedures, especially TSA inspection of the checked firearms in locked cases,designed to prevent? I can speculate, but does anyone know the actual reason ing behind the policy?