There is currently no way for the average end-user to increase "physical" view distances in this series. The real culprit is the limitation of the graphics subsystems, as you can only display distant objects down to one pixel. Doing otherwise (such as maintaining that single pixel .lod out to 20 km or so), is, in of itself, also quite unrealistic, as in the real world, you'd be able to resolve "dots", well below one pixel in size.
By far, the most believable solution to this, was the "sun glint" (canopy or skin-reflection) effect in MiG Alley.
Rest assured, we've all argued this point over at the developer's site.
As for the SR-71, yes, I do believe that it's a WIP, as is it's cousin, the YF-12 interceptor .