The STS-121 Flight Plan is the Flight Data File article that contains the on-orbit timeline. It does not contain the detailed timelines that are covered in the Ascent, Post Insertion, Deorbit Prep, and Entry Checklists.
Therefore, the quality of some images is degraded. Missing pages were either due to crew preference at fabrication, pages removed and not replaced during use, or errors during conversion to microfiche (in 1985).