Federal investigators are continuing to examine the crash of a vintage plane last year at the Reno Air Races. A World War II-era P-51 Mustang aircraft spiraled out of control and crashed while racing in September of 2011. The Mustang hit the ground right in front of the grandstand where thousands of spectators had gathered to watch the air races. A total of ten people died from the ground explosion and flying debris, and dozens more were injured. The plane was reportedly modified so that it could achieve speeds that exceeded 500 miles per hour.

This week, the National Transportation Safety Board released hundreds of pages of documents, photos, and other materials relating to its investigation. It appears that officials are focusing on some screws in the plane’s tail that may have been loose at the time of the crash. In addition, pre-flight inspections apparently revealed that some screws in one of the trim tabs was too short. The trim tabs are the mechanisms on a plane which help control its direction. Even though the crew supposedly addressed the issue and cleared the Mustang to race, officials lamented a lack of written procedures or verifications that states the problem had been repaired.

There have already been several wrongful death lawsuits filed in connection with this plane crash. Mechanical failure and pilot error are the leading theories about the cause of the tragedy. But it will likely be many more months (or perhaps years) before the federal investigation by the NTSB is complete.