The problem is most commercial operators here usually have jumpseat agreements with other operators, so their own personel can move about easily. This is normally on a reciprical basis.
It may be possible to do however. I have heard of Private Pilots getting in on the deck. You would certainly have to qualify as aircrew (hold preferable an FAA licence) as the FAA rule nobody allowed on the flight deck (during flight) who isn't a crewmember. It would also help if you are currently employed by an airline (company ID).