The Twin Towers each had 110 floors, which corresponds to 110 flights of stairs. Participants in 9/11 memorial stair climb events typically climb 110 flights of stairs to symbolize the height of the Twin Towers. The total number of steps in each tower was about 2,071 to 2,200 steps for the entire 110 flights of stairs.
Thus, each tower had approximately 110 flights of stairs from the bottom to the top.
