On January 2, 1998, at 1640 central standard time, a Mooney M20J airplane, N201LG, registered to and operated by the pilot, collided with trees following a loss of control while landing on runway 21 at Keystone Airpark, Westport, Oklahoma. The aircraft was substantially damaged and the private pilot, the sole occupant, was not injured. No flight plan was filed and visual meteorological conditions prevailed for the Title 14 CFR Part 91 personal flight, which originated from Poteau, Oklahoma, at 1550. In a written statement, the pilot reported that after an uneventful 50 minute cross country flight, he entered the landing pattern at Keystone and observed the windsock which indicated winds from 190 at 10 to 15 knots. He reported that, after a normal downwind, base, and final approach, he crossed the threshold and approximately 160 yards down the runway, the aircraft was about to touchdown when it started to veer to the left. The pilot attempted to stabilize directional control by applying right rudder and adding power. He stated that, a gust of wind then "lifted the right wing to a 20 degree" bank and turned the aircraft further to the left, which aligned the nose of the airplane toward some tree tops. Subsequently, the airplane impacted the trees, and settled to the ground, upright, and nose low. Examination of the wreckage by an FAA inspector revealed that the fuselage and empennage were buckled, and the right wing was separated at the root. The pilot flew the standard VFR pattern with 1/2 flaps selected on base and full flaps on final. He reported the winds at the accident site to be from 190 degrees at 12 knots, gusting to 15 knots. The reported winds at Tulsa, Oklahoma, located about 28 miles east of the accident site, were from 190 degrees at 16 knots, gusting to 25 knots. Inspection of the wind sock after the accident showed that it was intact and functioning properly. Examination of the aircraft by an FAA inspector after the accident did not reveal any preexisting control system anomalies that could have contributed to the accident. The pilot did not report any control problems with the aircraft during the flight.