On August 24, 2003, about 1245 central daylight time, an experimental exhibition North American AT-6, N37642, piloted by a commercial pilot, sustained substantial damage on impact with terrain when its left main landing gear collapsed during a ground loop at Offutt Air Force Base (OFF), near Omaha, Nebraska. The air show flight was operating under 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident. No flight plan was on file. The pilot was uninjured. The local flight originated from OFF at 1230 and was landing at the time of the accident. The pilot reported: I took off during the air show [at] 1230 and made 3 passes down the runway (12) [at] 400 [feet] and then set up for the landing on the down wind leg of the 4th pass. ... I made a smooth 3-point landing at approximately 1245, and on roll out the airplanes right wing came up and the airplane made a turn to the right. I was unable to correct before it slid onto the grass, at that point the left main gear collapsed, causing the wing and prop to hit the ground. The pilot reported thet there were no mechanical malfunctions prior to the accident. At 1255, the recorded OFF wind was 200 degrees at 8 knots.