American Airlines Flight 11
Because of the angle the airplane struck, people could not escape from at or above where the aircraft had crashed.  All stairs and elevators from the 92nd floor to at least the 99th floor were blocked by fire or debris, trapping 1,344 people. Hundreds were killed right away by the impact. The rest either were trapped and died from the fire, smoke or the collapse of the tower, and some even died after they jumped or fell out the windows of the burning building.  More than one elevator shaft carried the burning fuel downward, exploding on the way down.