Touchdown or no touchdown?

Question
According to NFL rules, if any part of the ball breaks the imaginary plane of the goal line, it is a touchdown. Does this imaginary plane extend out of bounds? In other words, if the ball carrier dives and extends the ball beyond the goal line on the outside of the sidelines while in mid air, is that a touchdown?

Answer
Yes John, what you describe would be a touchdown, provided the player is still inbounds, ie some part of his body was over the pylon.  The plane of the goal line stretches across the world, but it is "active" only so long as the ball carrier is inbounds.  If your ballcarrier leapt up, sailed throguh the plane of the goal line along the left sideline, with the ball in his left hand, as long as some part of him was inbouds, crossing the pylon - his right foot or arm say - it is a touchdown.  From the NFL Digest of Rules:

Touchdown: When any part of the ball, legally in possession of a player inbounds, breaks the plane of the opponent's goal line, provided it is not a touchback.