NameOmitted wrote:As I understand it, the development of the SP involved working out the aerodynamics of having the second passenger deck end over the wings. This led to a relatively inexpensive stretch of the passenger deck for the -300 and beyond.
As such, it was not so much an orphan made obsolete by the -200B or -400, but an integral part of the eventual success of the -400.
Yes, it opened up long range routes that the 747-400 later took over, and it created a benchmark for Boeing's 747-400 design team to match for designed range. The aerodynamic tweeks developed for the SP ended up being used on the 300 and 400.