Destruction of the Aircraft Remains at the WTC Site
The jetliners that impacted the North and South Towers became almost entirely embedded within them. No large parts visibly bounced off, and only a few parts emerged from the other side. The condition of the aircraft remains in the intervals between their impacting the building and its collapsing has been the subject of some speculation. The pattern of damage to the towers' exterior walls indicates that in both cases, the fuselage, engines, and wing roots punched through, and the wing tips were shredded by the grating of meter-spaced columns. Subsequent damage to the jets was determined by their different impact trajectories. The jetliner that hit the North Tower approached on a relatively centered trajectory perpendicular to the northeast wall, so that the parts that made it through the wall without being ripped up directly impacted the building's core. The jetliner that hit the South Tower approached on a similar trajectory relative to the southwest wall, but then swerved at the last second, so that it hit the right half of the wall at a rightward angle of about 20 degrees, allowing the fuselage and at least one engine to avoid the core.
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:
- Part of the fuselage on the roof of Building 5
- A piece of landing gear on a building three blocks north of the WTC
- An engine on Church Street three blocks north of the WTC
Piece of Flight 175 fuselage
Piece of Flight 11 landing gear
FEMA reported the following parts were recovered from Flight 11:
- a piece of landing gear on West Street five blocks south of the WTC
- life jackets and portions of seats on the roof of the Bankers Trust building
In addition to the aircraft remains documented in FEMA's report, there exist several photographs of jet engine parts, apparently from Flight 175, taken by pedestrians.
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.
Remains Trapped in the Towers
The majority of Flight 175 and the vast majority of Flight 11 remains were trapped in the towers and therefore suffered the same fate as the towers when they collapsed. FEMA's report is silent on what became of the aircraft "debris" that remained within the towers. Since whatever destroyed the towers converted nearly all the concrete to sub-100-micron powder, shredded the steel frame, and cremated most of the victims trapped inside, it is not surprising that it would leave little in the way of recognizable remains of the aircraft.
Even so, a recovery effort and investigation commensurate with the scale of the disaster would gather and catalog the aircraft remains with great care. This was apparently not done for the doomed aircraft just as it was not done for the collapsed buildings. The order of the day was to remove and recycle the evidence, not preserve and study it.