On November 12, 2007, about 0850 mountain standard time, a Piper PA-31-350, N84859, landed gear-up at the Salt Lake City International Airport (SLC), Salt Lake City, Utah. The commercial pilot, who was the sole occupant, was not injured, however the airplane sustained substantial damage. The airplane was registered to Spirit Air Inc. and operated by Salmon Air Taxi of Salmon, Idaho. Visual meteorological conditions prevailed and an instrument flight rules (IFR) flight plan had been filed for the Title 14 Code of Federal Regulations Part 91 repositioning flight. The flight originated from Carbon County Regional Airport (PUC), Price, Utah, at 0815. According to the pilot, he was initially inbound for a straight-in landing on runway 32, but the tower switched him to runway 35 after he had completed his pre-landing configuration items from memory. While on short final to runway 35, the pilot made a memory-based final configuration check, and it appeared to him that the landing gear position indicator lights were green. Soon thereafter he touched down on runway 35 with the landing gear still retracted in the wheel wells. Due to the fact that the gear was retracted, the airplane slid along the surface of the asphalt runway, resulting in substantial damage to the formers and stringers that make up the structure of the airplane's belly. During a telephone conversation, the pilot stated that during approach he felt rushed, and was communicating with the controller and watching other inbound traffic during the time period that he thought he had set the flaps, lowered the landing gear, and set the propellers. He further stated that he was not using a written checklist, but was taking the actions from memory. He said that he now realizes that what he thought were illuminated green landing gear position lights, was in fact a reflection of the rays from the rising sun.