WASHINGTON (WHTC News) - Nearly a year after it happened, the causes behind a plane crash that killed two Hope College students have been formally determined.

A probable cause report released by the National Transportation Safety Board showed that 23-year-old pilot David Otai was tired when he took off in a rented Cessna last January 17th from Tulip City Airport, with 20-year-old classmate Emma Biagioni as a passenger. Otai needed flight time in his quest to earn a full-fledge license so he could become a missionary in his homeland of Kenya upon graduation, and he had been offering rides to friends during these sessions.

Dense morning fog in the area confounded Otai, who hadn’t flown solely on instrument guidance in the two years since he had earned his pilot’s certification, and it led to the condition of “spatial disorientation,” similar to that suffered by John F. Kennedy Junior prior to his publicized fatal plane crash 12 years ago. Otai had contacted Muskegon County Airport air traffic control, asking for help, but his craft spun down uncontrollably and smashed into a field about four miles from Tulip City Airport, killing both he and Biagioni instantly.

The NTSB normally undergoes such a lengthy and comprehensive report after fatal crashes.