The National Transportation Safety Board's preliminary report into the deadly crash at a north Texas air show last month is now available. Six people were killed when a B-17 Flying Fortress and a P-63 King Cobra collided in midair at the Commemorative Air Force's Wings Over Dallas on November 12th. After an analysis of audio from the air show's radio transmissions, the NTSB says there was no discussion before or during the flight of flight information that would have reduced the risk of a midair collision. The report gave no direct reason for the crash. The agency says its full investigation could take 12 to 18 months.