Cockpit Chatter and Groundcrew Gripes

Some familiar, some not so
http://www.shartwell.freeserve.co.uk...round-crew.htm and the
first ever air accident report
http://www.shartwell.freeserve.co.uk...s-accident.htm !

Greetings to all.

I have run into a discussion whose answer is not clear. The question,
especially since 9/11, and its variant is:

Can passengers on commercial flights, during the flight, visit the
flightdeck (with captain's
permission, of course!)?

Essentially, is it the FAA or IATA that makes that determination or is it
air carrier policy?

Any links to the relevant documents would be greatly appreciated.

Thanks,
Charlie