On July 14, 2000, at 1130 central daylight time, an Ercoupe 415-C single-engine airplane, N99236, was substantially damaged as a result of a bird strike while in cruise flight near Stephenville, Texas. The airline transport pilot, sole occupant of the airplane, was uninjured. The airplane was owned and operated by the pilot and another private individual. Visual meteorological conditions prevailed for the 14 Code of Federal Regulations Part 91 personal flight. The flight originated from Longview, Texas, at 0830, and was destined for Stephenville, Texas. According to the pilot, approximately 20 miles east of Stephenville's Clark Field Municipal Airport, the airplane's right wing was struck by a "buzzard." The pilot reported that he observed the "buzzard" slightly above and to the right of his flight path. The "buzzard" dove into the airplane and the pilot was unable to avoid the collision. The "buzzard" impacted the top of the leading edge on the outboard section of the wing substantially damaging six consecutive wing ribs. The pilot added that the damage affected the flight characteristics of the airplane. The pilot was able to maintain control and landed the aircraft without further incident. The pilot reported the sky was clear, the wind was from the southwest at 12-18 knots, and the temperature was approximately 87 degrees Fahrenheit.