However, careful inspection of the photographic record reveals that the heavy column and spandrel sections from the collapse of WTC1 did not reach further than the southwest corner, and that the remainder of litter on the roof is exterior aluminum sheet-metal cladding, as shown in the photo of the Magic Fuselage. Having a high surface-to-volume ratio, cladding is incapable of achieving the terminal velocity to collapse a roof. Indeed, many of the steel exterior columns landing on WTC 6 did not even collapse its roof.
The photo above is cropped from FEMA photo No. 4271, facing southeast, and shows large circular holes centered in the building. A large section of penthouse, intact except for warpage caused by lack of support, overhangs hole (A), which appears to extend quite deeply into the building. This certainly makes it look as if hole (A) was removed from below rather than by debris hitting it from above.
Hole (C) is a collapsed section that appears to have been brought down by exterior tower columns hitting it.
Above, a shot of holes taken from directly above (north is up) show how circular hole (B) really is, looking more like a cavity caused by a central explosion than by debris falling on it, since the debris and the hole show little corelation. We suspect both holes are the same depth. That hole (B) seems so much shallower is probably an artifact of the additional lighting reaching it from the south.
This enlargement of a portion of a photo by Joel Meyerowitz also shows a general lack of the steel columns heavy enough to collapse a structure on the roof of WTC 5 in the region of the craters:
This further enlargement, the un-scarred roof segments overhanging the holes (arrows) suggest that the collapse originated from within:
