Mercury Dancer
Apologies for misunderstanding your direction of comment earlier, it seemed to me that you were saying any FD visitor was unfit from the perspective of proper control of the AC (which would have been the case pre 9/11). However, from your last comment it appears you were just saying that post 9/11 and SOP's having changed, that an FD visitor now would cause you concern then I agree.
As I said in my earlier post, if FD visits were re-instated even if just for children, it wouldn't take too long for someone with harmful intentions to exploit it.
As trains were mentioned earlier - does anyone know the current OP's of Trains & Ferries? I'm guessing these have changed as well for I remember as an 11 yr old travelling alone on B.Rail one day, being invited to complete my journey with the Train driver and briefely taking control of the train also (the Dead man's lever), also at 9 I had the fortune to be invited to the bridge of a ferry and had a go at steering that too. (That's if the OP's ever allowed this type of thing in the first place come to think of it). Combined with the aviation experiences I mentioned before, I was pretty lucky with childhood experiences.