Have you considered the possibility that the plane was coming apart because it was traveling at well above its maximum rated speed? Considering that it was diving, that's very possible, even likely.
That's what happened with the second WTC plane. It was doing about 100 MPH more than the first plane (about 475 MPH, IIRC), and pieces were coming off it just before impact.
Perhaps you were or still are unaware that this plane didn't go down for almost an hour after the last plane had hit the Pentagon. F-16's were airborne and were being vectored to this specific plane well before this plane went into the ground. Witnesses also at the time say a smaller plane was flying some distance behind the hijacked plane.
Look, if it was shot down by the USAF I'm not overjoyed that they had to do it (I feel horrible for the lives of those passengers and crew), but I'm thankful that our government has the guts to do what NEEDS to be done.