HISTORY OF FLIGHTOn June 29, 2017, about 0740 central daylight time, an Air Tractor AT602 airplane, N4196Y, was destroyed during an in-flight collision with terrain near Stirum, North Dakota. The pilot was fatally injured. The airplane was registered to and operated by Wilbur-Ellis Company as a Title 14 Code of Federal Regulations Part 137 aerial application flight. Instrument meteorological conditions prevailed in the vicinity of the accident site. The flight was not operated on a flight plan. The local flight originated from the Lisbon Municipal Airport (6L3), Lisbon, North Dakota, about 0700. An employee of the operator reported that the airplane was loaded about 0500. However, the flight was delayed about two hours while the pilot waited for the local weather conditions to improve. The pilot had spoken with individuals by phone before the flight to assess the local weather conditions. The employee noted that flying was limited to mornings in the days before the accident due to afternoon wind conditions. At the time of departure, the visibility was about 1-1/2 miles with overcast clouds, a light wind, and no precipitation. A witness reported that she was sitting on her patio when she heard the airplane. The sound of the engine was normal, "not anything unusual at all." She observed the airplane emerge from the fog heading east and "within seconds" impact the ground. The airplane was level or descending slightly and did not appear to change its flight path before impacting gradually rising terrain. She noted that the airplane did not appear to be out of control, nor did it seem that anything was wrong mechanically. She recalled that it was "very, very foggy" at the time, adding that she was just able to make out the outline of a prominent tree about 200 yards from the patio. There was no precipitation and little or no wind at the time. A second witness at the same location recalled hearing the airplane but did not see it. From the sound of the engine, the airplane seemed to be heading northeast toward Lisbon. It was "quite foggy" at the time; although, the fog had lifted somewhat from earlier in the morning. He estimated that at the time of the accident there was about 200 feet of relatively good visibility below the fog/cloud layer. He noted that the ground rises gradually approaching his property from the west; the elevation is approximately 56 ft lower about 1/2 mile west of his house. METEOROLOGICAL INFORMATIONAn airmen's meteorological information (AIRMET) advisory for instrument flight rules (IFR) conditions was in effect at the time of the accident. The accident site was located within, but near the southwestern extent, of the advisory area. The area forecast current at the time of the accident predicted broken clouds at 2,000 ft mean sea level and a visibility of 3 to 5 miles in mist until 1000 for eastern North Dakota. There was no record of the pilot obtaining a preflight weather briefing through Lockheed Martin Flight Service, the Direct User Access Terminal Service (DUATS), or Foreflight. However, it is possible that the pilot obtained weather information from a commercial service that did not track the activity to a particular pilot or aircraft. WRECKAGE AND IMPACT INFORMATIONThe airplane impacted a soybean field about 14 miles west-southwest of 6L3. No obstacles such as large trees, power lines, or transmission towers were located in the immediate vicinity of the accident site. The main wreckage came to rest about 150 ft from the initial ground impact crater; the overall debris field was approximately 280 ft long. Ground marks consistent in appearance with propeller slashes were located near the impact point. A ground depression and impact scar were located immediately adjacent to the impact crater. The depression appeared consistent with being formed by the right main landing gear. The right aileron counterweight was separated and embedded into the ground near the end of the impact mark. A postaccident examination was conducted by Federal Aviation Administration (FAA) inspectors, assisted by a representative of the airframe manufacturer. No anomalies consistent with a preimpact failure or malfunction were observed. A detailed summary of the examination is included with the docket material associated with this accident investigation. ADDITIONAL INFORMATIONIn response to the accident, the National Agricultural Aviation Association issued an advisory to member operators as part of the Fly Safe Campaign. The advisory warned pilots regarding the hazards of low-level instrument conditions and the importance of a thorough preflight weather briefing. MEDICAL AND PATHOLOGICAL INFORMATIONThe University of North Dakota Forensic Pathology Office, Grand Forks, North Dakota, performed an autopsy of the pilot. The pilot's death was attributed to blunt force trauma sustained in the accident. The FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology testing on specimens of the pilot. Testing was negative for all substances in the testing profile.