The Pentagon was in a renovation process on September 2001. The sixty years old building needed some lifting. Among the modifications, a reinforcement was made to protect the building against an attack. Vertical steel beams were added to reinforce the external walls. Internal pillars were wrapped with kevlar. New windows were disposed in the openings, with anti blast transparent material : each window weights 2000 lb and each glass is near two inch thick ! Clearly, the firing of any bullet or small missile, like for example a hand held anti aerial missile, would have only scratched the external skin of this part of the building, like the firing of a RPG missile made a hardly visible damage on a nuclear plant building in France in the seventies. It was a common subject of laugh in the Pentagon to say that the "E" ring (the external ring) being the place where the highest ranking military personal have their offices (the only ones with view towards the building's environment), it was normal to expend the taxpayer's money to protect them...

The hasard - or another reason - did that the attacking plane ran into this newly renovated part of the pentagon on september 11. The zone struck by the attacking plane was reserved to the navy. On the first floor, had just been installed a new communication center.

The pictures below, some seen on the first images analysis page of this site, show the impact on the front, before this section of the Pentagon collapsed.

façade 1 façade 3
façade 2 façade 4
façade 5 façade 6

It's difficult to see the impact zone, because during the 40 mn beetween the crash and the collapse, the lowest part of the building front was most of the time masked by the water or foam thrown by the fire trucks. This has led a lot of people to think that the hole made by the fuselage of the plane was the 5 m x 4 m hole which can be seen on the second floor. In fact, this hole is just the upper part of a much bigger hole which extends from ground level. At the first floor level, this hole is as large as the body of a 757, and even more if we consider that it extends on the left where the port wing was. The first / second floor slab is completely damaged, the right part hanging just hold by the steel reinforcements. A reconstruction of the front of the building, using several pictures has been done by XOX . On this reconstitution, a silhouette of plane has been drawn, corresponding to the damage seen on the building. It is necessary to note, to understand images lower in this site, that the Pentagon is a modern building where all the structural efforts are supported by an array of pillars. These have been numbered, since the time of the construction, with letters from AA, A, B, ... going from external to internal rows, and digits (1, 2, ...) corresponding to the location on the front, the digit range being applied to each "wedge" (angular sector of the pentagonal shaped plan). The numbers at top of building's front are the pillar numbers. The image is interactive : click on the checkboxes to hide / draw the layers.

Plot : 

The fuselage and wings diagrams drawn on this pictures are only a way of locating the damaged zones, and don't represent, at least taken as a whole, the silhouette of the plane. For the starboard wing, two hypotheses have been drawn :

The first case would correspond, roughly, to a Boeing 737 wingspan, the second one to a Boeing 757.

It is clear, looking to this sketch, that in the maximum extent damage hypothesis, the port wing damage has much less horizontal extension from the fuselage (or nose impact point) than the starboard one The damaged zone on the front goes at least from pillar 8 to pillar 20, the impact zone being close to pillar 14. At the maximum, it goes a little farther than pillar 22, i.e. twenty feet more in extent.

The extreme part of the port wing damage can be appreciated on the following images.

Left wing hole Left wing damage

It seems obvious that the completely ripped exterior wall and columns account for a very violent impact that has "punched" the hole properly, leaving only what seems to be kevlar reinforcement hanging from the ceiling. One of the serious researchers on this crash, Sarah Roberts, has seen this problem of "missing port wing tip damage". She conjectured that this part of the wing has impacted at the first / second floor slab level, giving the damage seen on the photos above. I don't agree with her on this point. I think that these damage and those visible on the pillars between the intact windows are due to the shockwave which propagated through this slab. This slab is completely destroyed on the whole width of the fuselage, around the impact point. A very strong explosion / shock is necessary to destroy a slab this way. The shockwave created must be able to propagate laterally in this slab and give local destructions, not so strong however : the loss of the external limestone parement is the clearly visible (but structurally minor) damage. Let me remind that witnesses located at the other side of the Pentagon felt the whole building shocked...

For the starboard wing, it's necessary to precise things, examining the Pentagon's facade in the zone of the impact on a closeup.

Plot : 

It could seem rather odd, at first sight, that the starboard wing could possibly have an extent like plotted on this image. But several facts can excuse the rather light damage on the Pentagon's front, including the fact that a window beetween pillars 21 and 22, apparently stroken, has not been broken.

Here are two other images. Click on the checkbox to enlarge.

Conclusion

The "too small hole" for a B 757 to have penetrated inside the Pentagon can be explained this way for the starboard wing. For the port wing, it is mandatory to take into account the folding of the wing along the fuselage, which will be detailed in the next section. If these explanations don't stand, it will be necessary to make the hypothesis that the plane was a little smaller, like for example a B 737. But in any case, it could not be a smaller object, like a F 16, a cruise missile, ...