Where airlines allow passengers to board before flight deck crew, is there a rule that when this happens the flight deck door must be locked (or otherwise guarded)? I'd hate to think that the flight deck could be accessible to passengers
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P.S. I remember being a passenger on a US Airways 'plane which made an en route stop at Pittsburgh. I was the only person who chose not to get off and stretch his/her legs. When we took off for Charlotte I discovered that not all the cabin crew could leave the aircraft because of me; if I'd known this, I'd have gotten off, too. I felt sorry for them!