The flight instructor’s inadequate supervision of the flight, which allowed for an unintentional movement of the mixture control to the cutoff position that remained unnoticed until the airplane lost engine power due to fuel starvation and descended below the minimum altitude required for a normal deployment of the airframe parachute system. Contributing to the accident was the impairment of the pilot due to his illness, the flight instructor being distracted by his physiological distress, and the apparent lack of communication between the pilot and flight instructor about who was responsible for the safety of the flight, all of which created a situation where neither individual was adequately monitoring the engine operation during a critical phase of flight.