According to the report handed by the federal investigators to the National Transportation Safety Board, it seems that the plane crash was caused by poor maintenance of the plane before take-off, as well as the lack of a record-monitoring process by the NASCAR.
It seems that the plane had some problems when piloted the day before the crash. According to the aforementioned source, “the pilot who flew that Cessna (the plane) the day before the crash turned off the radar system and pulled its circuit breaker in mid-flight after he began smelling a burning odor.” However, the pilot managed to safely land the plane, while immediately proceeding to filing an accident report to the NASCAR.
And this is where it all started to go wrong. Due to NASCAR airline's poor data-recording process, the accident report filed by the pilot a day before the actual crash was never found. Nobody knew anything about the incident. So when the new pilot came in the next day, while knowing there was something wrong with the plane – as he might have noticed the turned-off radar – he didn't think it was that serious and took off without thoroughly investigating the problem.
According to the same report, it seems that an electrical problem occurred during the fly, which led to a fire on board. The plane eventually went down and crashed into a house in the Sanford region (Florida), killing the 2 people on board – the pilot and Dr. Bruce Kennedy, the husband of NASCAR executive Lesa France Kennedy – and 3 on the ground (2 children included).