After a careful review of all the facts that I've had at my disposal, I still have no idea what exactly happened.
But I have concluded that IF TWA Flight 800 was brought down by a missile, it was not an act of terrorism -- it was shot down by a naval vessel off the south shore of Long Island that night. In the immediate aftermath of 9/11 it suddenly occurred to me that it may have been brought down deliberately after the U.S. government got wind of a 9/11-type suicide attack in process on board the plane, but after going through many fascinating threads here on FR about this subject I concluded that it was almost certainly an accident.