[KellyAdmirer]

That's good video footage, thanks. If tiles are as fragile as they say, I think a chunk of just about anything hitting at that speed and spraying like that must have the potential to do some serious damage if it hits the right spot.

[Fury]

In watching the video, it appears the debris which traveled under the left wing of the shuttle was not in the same state (smaller pieces) as it was prior to traveling on the underside of the left wing (a solid piece or pieces).

[jdege]

The shuttle has landed, though, in the past, with several tiles damaged.

I expect that there are certain tiles that are more critical than others - perhaps it was one of these that was hit.