The amount of damage done the the pentagon is far more severe than an F-16 mounted air-to-air missile could ever produce. Airforce missiles do not have the fancy paint job shown in the photo, nor the thin, aluminum skin present in the photo. The missile story is bogus, internet rumor, urban legend, et al.
One other small problem with the missle/no plane theory. Several thousand people on 395 and the adjacent roads witnessed the plane hit the building. I have personally spoken with one eye-witness who will NEVER forget the site of a plane moving at that speed and height.