The eyewitnesses would perceive it as an object rising up from the Earth to hit something.
Ever been in an airplane struck by lightning? Happens with some frequency BTW. Every now and then lightning will take a plane out of operation.
Here we have a rock flying in from space and taking out a plane. Won't happen all that often, but it can't be ruled out.
As I stated triangulation of eye witnesses show that it could not have been a bolide. Only eye witnesses looking at a bolide ~180º from its direction of approach will see it rise from the horizon... others would see it approach horizontally across the sky. That was NOT the case. Ergo it was not a bolide.
Eye witnesses West of TWA800 saw it come from the surface. Others that were North saw it come from the surface. More from the South saw it rise from the surface. And yet others who were East of the plane saw the "missile" rise from the surface. If it were a bolide, only 1/4 of these would mis-perceive the object as coming from the surface.
Certainly some of the eye witnesses who were in the air, above TWA800, would not have described it as they did were it a bolide.