Cockpit doors

I’d be interested in learning whether the reinforcing of cockpit doors was discussed before 9/11, whether by the companies, unions, FAA, etc. I have heard suggestions that the issue was actually placed on the table by the FAA, but beaten back by the airlines–only to be hastily revived on 9/12/2001. Anyone’s recollections gratefully received.

Please don’t post the same subject in two different forums.