The pilot failed to extend the landing gear and the airplane landed gear-up. The 7,576-hour private pilot informed local police and the NTSB that he "simply forgot" to extend the landing gear prior to landing on the 4444-foot-long, by 75-foot wide asphalt runway. The single-engine airplane landed on its belly and skidded to a stop before a fire erupted. The pilot and his passenger were able to egress the airplane and were not injured. The pilot, who reported having accumulated 6,626-hours in the same make and model, reported that he did not recall hearing the sound of the landing gear horn prior to touchdown and suspected the horn may have not worked. Examination of the airplane by an FAA inspector revealed that the airplane sustained extensive post impact fire damage, and the landing gear handle was found in the retracted position. The accident occurred at the conclusion of a 45 minute cross-country flight.