I was working at LAX when they first moved the WTMD from the airport gates down to the bottom of the escalators (for those who know LAX layout).

That is, they were originally located at the entrance to the gate to the planes. Then, during the middle of the summer (I think it was 1971, but maybe 1972) they suddenly moved them down to the bottom of the escalator at the end of the walkway. (History - LAX was a single layer airport until the 80's. Those "lower level walkways" were the only walkways. Planes went to round terminals and could drive "over" the passenger walkway.)

At that time, any airport employee with a photo ID was exempt from screening. I was working as a busboy/waitress (first male waitress at LAX) and refused to come to work, unless I got a photo ID, because I wasn't getting on an airplane so, IMHO, there was no 4th Amendment basis to screen me. The head of security for Host, who was under instructions not to give photo ID to hourly employees (they cost $5 each) met with me, liked me, and said "I am not going to lose a good employee. You can have a Photo ID."