
In response to the question of "where is the wreckage of the plane", the answer is that much of the wreckage slid into the ground floor of the Pentagon. It slid INTO the building, into the first floor space, starting a fire in the first floor, whereupon the upper floors later collapsed down onto the remains of the aircraft. Most of the aircraft wreckage is therefore under the collapsed roof section in the photo.
So where is the rest of the wreckage from the passenger plane? Right in plain view, for those who actually look.

In the above copy of the wide area view, a red rectangle marks an area to be examined. This area appears below.
Click for larger image of the insert
The Pentagon is a building mostly made of concrete and wood. Yet here is a pile of crumpled aluminum debris, and clearly seen mixed in with it are pieces of luggage. Since the Pentagon itself does not travel, we can conclude that the luggage (and the aluminum shards mixed with them) are part of the remains of the passenger jet which hit the Pentagon.
In similar crashes, the resulting debris was in small pieces, 6 feet long at most. You don't SEE huge pieces of airplane sitting at crash sites in head on collisions such as slamming into the wall of the Pentagon. Despite their impressive size, aircraft and relatively fragile objects due to weight considerations.