OT

I have occasionally seen dual jetways (jetbridges) in use (both on the left side of the plane), HNL comes to mind.

One small charter/LCC airline called World Airways (WO) back int he 1980's used stairways rather than jetways for their DC-10's , and occasionally had two stairways in use, one at the front or center and one at the rear, again on the left side only. Since pax were so accustomed to, and positioned their baggage for, front disembarking, the rear stairs did not work well in most cases.

Travel tips:
http://members.aol.com/ajaynejr/travel.htm