There were no traces of UA93 or UA175 planes at "crash" scenes (George Nelson)
Officials claimed to have obtained sufficient human remains to match with DNA samples (various media sources)
UA93 and UA175 flew after times of "crashes" (Pilots for 9/11 Truth)
Were any human remains really identified at the scene of Shanksville? Here is one of several news articles that says so.
We can also establish
that the FBI was in charge of area, giving the agency the authority to
declare who could and who could not go on the "crash scene" area.
How were victims at the "crash" scenes "identified"?
DNA testing requires sample from a victim at the "scene" and a sample
from victim from somewhere else (usually given by family).
An agent (of the plot) would likely retrieve sample from the "scene" of the victim's death.
Agent would give samples to the tester. (The tester, as one who would
follow standard procedures, would not have any reason to go to the scene
nor to question the Agent).
The agent would also go to the family to ask for samples (ex: hair, toothbrush, etc.)
The agent would then give the family sample to the tester.