The exact cause of the accident was never determined. At the time of the accident, 90% of the flight test program had been completed, over the course of 42 flights with a total flight time of 20 hours, 15 minutes.
The exact origin of the crash remained unclear. By the time of the accident, 90% of the flight testing schedule had been completed, encompassing 42 flights that collectively lasted 20 hours and 15 minutes.