On December 3, 2008, about 1315 central standard time, a McDonnell Douglas DC-9-50, N782NC, operated as Northwest Airlines (NWA) Flight 1742, and piloted by an airline transport pilot, sustained substantial damage when it was struck by a tug. The aircraft had just landed on runway 36 at the Dane County Regional Airport-Truax Field (MSN), Madison, Wisconsin, and the flight crew requested a tug to tow the airplane to the gate due to taxiway conditions. The Title 14 Code of Federal Regulations Part 121 flight was operated in instrument meteorological conditions and was on an instrument flight rules (IFR) flight plan. No injuries were reported. The flight originated from the Detroit Metropolitan Wayne County Airport (DTW), Detroit, Michigan, at 1117. MSN was the intended destination. According to a report filed by the operator, the airplane landed on runway 36 at MSN about 1236. The pilot was directed by air traffic control (ATC), to exit the runway at taxiway A1. The aircraft slowed to a safe taxi speed and attempted to exit at the taxiway, but missed the taxiway and stopped about 6 feet onto the runway overrun area. The pilot contacted ATC, and requested permission to execute a 180-degree turn on the overrun. During the turn, the airplane began sliding on the snow and the flight crew stopped the airplane about 90-degrees into the turn. The airplane was facing west and was still on the paved overrun area at this time. At this point, the pilot contacted ATC and requested a tug to pull the airplane to the gate. A NWA tug was dispatched and an airport snow removal truck spread sand on the area between the nose of the airplane and its left wing. After the tug was attached to the airplane and had started to move, the airplane/tug jackknifed and slid on the snow covered runway. The tug impacted the left side of the airplane's fuselage causing a puncture to the skin and damage to internal structural members. The tug was subsequently re-connected and the airplane was towed to the gate where the passengers de-planed normally.