I have seen various clips from this video/dvd posted up on ATS.
The documentary as a whole is extremely interesting and has a lot of good case's in there.
The first thing I though when I saw them join was that the closer one (the top one in the photo) simply covered the other object. I'm gussing both
objects are the same size, simply one is closer than the other...
Of course what the objects are is hard to say, as they don't look like any conventional aircraft that I'm familiar with...