That was reported shortly after the crash. Before the plane was delivered to AA, a detailed examination found signs of delamination near one of the six vertical stabilizer attach points. A standard composite repair was performed consisting of metal doubler plates bound by rivets. This has been the standard repair method for composit structures for a long time. The repair apparently held all of those years and it appears the failure was just above the doublers. I don't know of any other cases where a composite structure failed like what happened in that accident.

I read an interesting article last month about aviation safety. The author stated that most of the "normal" causes of airline accidents have been engineered out of airplane designs. What we're seeing now are the freak accidents like TWA 800 fuel tank explosion, the Swiss Air crash (apparent fire due to old wiring), Alaska Air crash due to worn jackscrews, pilot error due to fatique (the Little Rock and Guam crashes come to mind), etc. I don't know if the author is right or not but it's interesting to think about.

I just found a link to the article I mentioned in my earlier post. If this link doesn't work, go to the Washington Post or MSNBC websites and look there. The article also mentions flutter as a possibility, perhaps triggered by a malfunctioning yaw dampener.

BTW: for anyone interested, the black parts seen in the photo are the composite fibers. Carbon (graphite) fibers are black.