They were probably transported to Det 3/Groom Lake, and then later
Tonopah that way, by C-5 from the Lockheed factory at night.

I think Travis AFB has some C-5 crews specially designated to take
certain cargo from places like Skuny Works, out to the ranges.

There's reason to believe that there was at least one C-5 configured
to haul some NRO monstersats (KH-11 and descendants), plus the related
HST from Lockheed Sunnyvale to the Cape. So it seems reasonable that
there would be a requirement to haul black aircraft also.