True, but the illusion of open airspace might not actually require that much space. It's pretty amazing what we can do with VR already, and I imagine the technology has the potential for a few more decades of substantial refinement before hitting any sort of plateau. Of course, tricking the part of your brain that hates living in a space coffin isn't necessarily as easy as tricking the part of your brain that wants to pretend to be a space marine for twenty minutes.