The 5-foot piece was initially thought to be a piece of landing gear, but officials later determined it was a trailing edge flap support structure. Located close to the body of the plane, the part helps secure wing flaps that move in and out and aid in regulating speed.
Boeing officials told police the part came from one of its 767 airliners, but it isn't possible to determine which one. Both hijacked planes that struck the towers, American Airlines Flight 11 and United Airlines Flight 175, were Boeing 767s. American and United have had no comment.
The medical examiner's office sifted through sediment at the site for days, but found no potential human remains.
Investigators continue to recover potential human remains from the trade center construction site. About 3,000 people died in the attack, and 1,000 were never identified.