NTSB is finally beginning to examine the possibilites of terrorist act for the WTC aircrashes, rather than pilot error. At first the NTSB was disinclined to believe eye witnesses as all know eye witnesses, from pyschological shock and the ability of light to travel fatser than sound, often see explosions and crshes in reverse order. The NTSB was examining in detail the possibility that an explosion at the WTC ocured prior to the airplane crashes, despite the eyewitness claims - many who are firemen and policemen.
However, the NTSB is now starting to examine the possibility of a terrorist act given that "we are at war" and gven the recent "shoe bomber", caught in the act trying to blow a hole in the AC during flight.
The NTSB is starting to consider that their peacetime protocal might not be sufficient during time of war.