On September 2, 1999, at 1715 central daylight time, a Weatherly 620B agricultural airplane, N4660M, was substantially damaged during a forced landing following a loss of engine power near Big Spring, Texas. The airplane was registered to and operated by Bruton Aerial Spraying, Inc., of Garden City, Texas. The commercial pilot, sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed for the 14 Code of Federal Regulations Part 137 aerial application flight. The local flight originated from the Big Spring McMahon-Wrinkle Airport, Big Spring, Texas, at 1625. According to the 16,361-hour pilot, he was applying malathion to a field when he noticed that the fuel warning light for the right fuel tank was illuminated. He switched the fuel selector from the right tank to the left tank, and "shortly thereafter [the] engine began cutting out and missing." He turned the auxiliary fuel pump on, but subsequently, the engine "coughed and quit." He executed a forced landing to a field where the airplane collided with a five-foot-high dirt terrace and came to a stop upright. The operator reported that the pilot stated that the aircraft "ran out of fuel." An FAA inspector examined the airplane at the accident site. The inspector stated that the left main landing gear penetrated the wing structure, and the left wing spar was damaged. The engine mount was "sheared off." There was a "trace of fuel" in the right wing fuel tank, and the left wing fuel tank was "complete[ly] dry." He added that there was no fuel present in the main fuel line, and there was no fuel present in the carburetor. He stated that the integrity of the fuel system was not compromised.