The recent release of hundreds of pages of National Transportation Safety Board documents still leaves many unanswered questions about what happened to the flight that killed Paul Wellstone and seven others last October. It will likely be months before the NTSB issues a final report on the crash. Although no clear cause has yet emerged, several areas stand out as possible factors. They include weather, pilot incompetence and problems with navigational equipment at the Eveleth- Virginia Airport. Minnesota Public Radio's Mark Zdechlik reports.