The Boeing website illustrates a seating layout that accomodates 200 passengers. However, the American Airlines 757-200 that was Flight 77 probably had a seating capacity of 188. See the table on the Commandeered Flights page.

This detail is not important for this talk, but it and a related detail -- that a United Airlines 757-200 such as was Flight 93 probably had a seating capacity of 182 -- contradicts an assumption of some of the plane-swap speculations that one of the 757s had a seating capacity of 200.