Glad to see that time machine project is working out.
Funny things are everywhere.
Not only is remote control technology much better, but automated landing technology is also much better. So I don't think landing the D-21 would be a big problem today. The 'mishap' happened in 1994, not 1995. There isn't much air at very high altitude, so you have to compensate for it somehow. Most aircraft accomplish this by inserting turbochargers between the inlet and engine intake manifold, but this is only practical up to a point.