On December 23, 2006, about 2145 Alaska standard time, a Boeing 747-228F airplane, N752SA, sustained substantial damage when it was struck by a deicing truck during deicing at the Ted Stevens Anchorage International Airport, Anchorage, Alaska. The flight crew was aboard preparing the airplane for flight. The airplane was being operated as Flight 996, by Southern Air Inc., Norwalk, Connecticut, as an instrument flight rules (IFR) non-scheduled domestic cargo flight under Title 14, CFR Part 121, when the accident occurred. The three flight crew members were not injured. Instrument meteorological conditions prevailed, and an instrument flight plan was filed. The airplane departed Anchorage about 0030, and was bound for Dallas, Texas, but returned when the crew was unable to pressurize the cabin. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on December 26, the FAA inspector who examined the airplane, reported that after the airplane departed Anchorage, the flight crew discovered that the cabin would not pressurize, and they returned to Anchorage and landed. The inspector said during an inspection of the airplane, maintenance personnel found a penetrating gouge in the right lower portion of the fuselage between the wing and tail, near the cargo door. The inspector indicated that the penetrating gouge was 18 inches long, 1 to 2 inches wide, with other, shallower surface skin damage about 3 feet long. He said the damage was consistent with the size and shape of the counter-balance weight on the truck used to deice the airplane.