Weather may have been a key factor in the Minnesota plane crash which killed three central Iowa men yesterday. Radar approach controlers had the twin-engine aircraft on its screen and told the pilot his approach was too low. Somewhere in its turn, the airplane hit the ground, about five miles outside of Moorhead, Minnesota. Rescue crews searched for an hour and a half before finding the crash site. National Transportation Safety Board air safety specialist John Brannen says heavy fog may, indeed, have been a factor in the crash.