<font face="Verdana, Arial, Helvetica" size="2">I stand to be corrected here but I believe that it is against Fed regs for anyone to travel in the jumpseat unless a pilot within that airline. Not sure if that only applies in US airspace though.
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Applies worldwide. Pilot's on other US carriers are also allowed, subject to restrictions in the airline's op-specs.
As someone else said: you can likely get a visit while still at the gate if they are not too busy and you ask nicely (or even better, if there is a long delay for pushback and everyone is sitting waiting...)