ALVERTON, N.Y., Oct. 27 — After T.W.A. Flight 800 exploded over the Atlantic Ocean off Long Island in 1996, an old airplane hangar here became a sacred place. Investigators pulled mangled hunks of what had once been a Boeing 747 from the ocean, hauled them to the hangar and began piecing them back together in one of the largest reconstruction projects in aviation history. Over the years, people visited the wreckage and laid carnations on the seats where their daughters and husbands had died. Some called the site a tomb; others said it was a monument to their loss. Now,...