Flight 77, the supposed plane that hit the Pentagon on 9/11 was a Boeing 757. It is the same plane that President Trump flies in.
A Boeing 757 uses one of 2 different engines: Either a Rolls-Royce RB211 or a Pratt & Whitney PW2000
Here is a diagram of a Rolls-Royce RB211. It says the opening of the turbine of a RB211 is 84.8 inches in diameter. (7 feet)
https://ars.els-cdn.com/content/image/3-s2.0-B0122274105003562-gr7.jpg
Here is a photo of President Trumps plane (757), look at the size of the opening of the plane turbine and the person standing next to the plane. Look at the center hub of the turbine, compare its size to the person standing next to the plane.
Here is a photo from the Pentagon on 9/11. Look at the round object behind the person on the left. That is the center hub of a turbine from the object that hit the Pentagon. Notice anything wrong?
This picture of a cutaway RB211-535E4 may help. The large fan is on the front but the part you can see in the Pentagon photograph has a shroud round the outer edge. I believe this picture shows guide vanes but turbine blades have a similar shroud round the outside.
To me, the Pentagon image seems to be of shrouded blades which implies turbine blades rather than compressor blades. In the cutaway picture the compressor sections are on the left and the turbine sections are on the right. The combustion chamber is in between.