The question on the Pentagon airplane or airplanes is, I think, complicated. A number of apparent conflicts in lines of reasoning has made it difficult for me to settle in on one set of consistent answers. For the past several years, I have favored CIT's north-path airplane with flyover. This hypothesis implied, I thought, either no airplane struck the Pentagon, or an airplane struck in tight time correlation with the flyover airplane.
Recently, I've taken a more careful look at many of the issues, and have gradually shifted my thinking toward an airplane impacting the Pentagon. One shift was deciding the north-path airplane was more likely not time correlated with the explosive event at the Pentagon face.
Another shift came relative to the "no debris on the lawn" issue. I was bothered the "no-Boeing" folks didn't have much of a comeback to the Sandia F-4 sled test implications. That test provides empirical evidence suggesting that "confetti" is what should be expected when an airplane crashes at high speed into a hardened wall.
An "ah ha" moment occurred when I ran across a photo in a different setting with "confetti-like" debris on the ground. I was familiar with the photo, as Jim Hoffman described the photo as "...portion of the lawn near the heliport." I stumbled across the same photo in the book, Pentagon 9/11, but the ledger read, "...debris-covered helipad." The helipad, it turns out, is in the exact right spot for deflected debris from a plane flying directly over the cable spools before impacting the Pentagon centered on column 14, the official impact column. This gave a boost to the 757-on-south-path hypothesis.