On April 18, 2000, at 1948 central daylight time, a Beech 58, N9429Q, owned and operated by the Gailforce Corporation, Janesville, Wisconsin, sustained substantial damage during a wheels-up landing on runway 18 (5,299 feet by 150 feet, dry concrete) at the Decatur Airport, Decatur, Illinois. Night visual metrological conditions prevailed at the time of the accident. The cargo flight was operating under the provisions of 14 CFR Part 135 and was on an active instrument flight plan. The pilot, the sole occupant, reported no injuries. The flight departed the Greater Peoria Regional Airport, Peoria, Illinois at 1915. According to the pilot's written statement, "...reached for the gear handle but for some reason I must not have selected gear down." The pilot continued, "Assumed the gear was down and continued with the landing. Flared to land with no gear and it settled on the belly maintained control with rudder and full back elevator." The pilot stated that the accident could have been prevented by, "use of checklist." Members from the Decatur Airport Fire and Rescue Unit and the Fix Base Operator examined the airplane at the Decatur Airport. The landing gear handle was found in the "up" position. The airplane was then raised and placed on jack-stands. When the landing gear handle was positioned to "down" the gear extended normally and the three green lights on the instrument panel illuminated.