ALLEGAN COUNTY -- The reason for the crash that killed two Hope College students Sunday remains a mystery. The NTSB has begun their investigation. Pilot David Otai was rated to fly on instruments, and multi-engine planes and hoped to one day fly missionaries around his home country of Kenya. He had rented planes before from Tulip City Airport, trying to log flight hours to earn his certification. The plane had logged about 40 hours in the air since its last inspection. There may be some clues in the distress message that Otai radioed in before the crash, but that has not been released. Otai, and passenger Emma Biagioni died in the crash.