Somewhat quoting the guy you quoted with a CDL. I have a Class B CDL with HazMat endorsement. I had to pass through both and FBI and TSA background check to get the HazMat endorsement. When I go to the airport, I should be able to flash my DL that has the HazMat Endorsement and walk right through security. After all, its what the TSA agents get to do, so why can't I? I passed the SAME background check the TSA agents have to pass to become employed by the TSA.

