Remains Exiting the Towers
One of the few, if only, official documents detailing the remains of the aircraft is FEMA's
World Trade Center Building Performance Study . It documents some aircraft parts that passed entirely through the buildings, landing some distance away. FEMA reported the following parts were recovered from Flight 175...
That these remains (excluding the passport) passed through the buildings is consistent with the fact that landing gear and engines are the densest parts of jetliners, and that having missed the core, the fuselage of Flight 175 had enough momentum for some of it to make it out of the tower by punching through the east corner of the tower's wall.