The Official Account
The 9/11 Commission reported that United Flight 93, having been taken over by an al-Qaeda pilot, was flown at a high speed and steep angle into a field near Shanksville, Pennsylvania. 
In response to claims that United Airlines Flight 93 was shot down, the US military and the FBI said that United 93 was not shot down.
The Best Evidence
Residents, the mayor, and journalists near Shanksville reported that no airliner was visible at the designated crash site;  that contents were found as far as eight miles from the designated crash site;  and that parts — including a thousand-pound engine piece — were found over a mile away. 
References for Flights Point 2
- The 9/11 Commission Report, 2004, p. 14.
- “9/11 Flight 93 Shanksville: Mayor Says No Plane Crashed!.”
“9/11 Flight 93 Shanksville: No Plane! No Crash!” A 1994 US Geological Survey showed the same crater and scar that was allegedly left by the crash of Flight 93.
“Flight 93 Crash Exposed: Rare Footage Never Again Seen on TV.”
“Nothing there except a hole in the ground.”
- Bill Heltzel and Tom Gibb, “2 Planes Had No Part in Crash of Flight 93,” Pittsburgh Post-Gazette, September 16, 2001: “Debris from the crash has been found up to 8 miles from the crash site.”
“America Under Attack: FBI and State Police Cordon Off Debris Area Six to Eight Miles from Crater Where Plane Went Down,” CNN, September 13, 2001.
Debra Erdley, “Crash Debris Found 8 Miles Away,” Pittsburgh Tribune-Review, September 14, 2001.
- Richard Wallace, “What Did Happen to Flight 93?” Daily Mirror, September 12, 2002.
For further discussion, see David Ray Griffin, The New Pearl Harbor Revisited, 2008, pp. 120-21.