[shorty_harris]

...Due to the fact that the newest SOFIA platform is a 747, it has lots of room for scientists and equipment compared to previous platforms like the C-141A prototype plane.

The most important difference is that it has a primary mirror 3 times the size of the Kuiper Airborne Observatory.

[Paleo Conservative]

The most important difference is that it has a primary mirror 3 times the size of the Kuiper Airborne Observatory.

Which was about as big a telescope as could be fit in a C-141. Being the C-141 prototype, there were enough idiosyncracies in its configuration to make it not worthwhile to convert to the stretched C-141B configuration. It was one of just a handful of surviving C-141A's to not be converted back in the late 1970's early 1980's.