the instructor's improper in-flight planning/decision making and fuel mismanagement which resulted in fuel starvation/exhaustion, the loss of engine power and the subsequent forced landing. Contributing factors include the instructor's inadequate preflight planning/preparation and the lack of suitable terrain for a forced landing.

The failure of the pilot of N331DM to maintain a proper visual lookout and ensure adequate clearance, which resulted in a collision with N11938. A factor in the accident was the failure of each pilot to communicate with the other.