The Pentagon was struck in the exact and only part (i.e. Wedge One) that had been undergoing renovations which were completed, or neared completion, on the very morning of 9/11.
Curiously, it was the exact opposite side as the side that housed senior leaders. The renovations made that part of the Pentagon the only part with blast resistant windows and a sprinkler system. It was ostensibly the safest part of the Pentagon. If that was the safest part of the Pentagon, why did none of the senior leaders seek shelter in that part of the Pentagon?
See: http://articles.latimes.com/2001/sep/16/news/mn-46435
See: http://911research.wtc7.net/pentagon/renovation.html
See: http://911research.wtc7.net/pentagon/analysis/location.html