On January 19, 2006, approximately 1115 mountain standard time, a Boeing B777-200B, N798UA, owned and operated by United Airlines, sustained minor damage when it was struck by a de-icing truck at deicing pad 3W, Denver International Airport (DEN), Denver, Colorado. Instrument meteorological conditions prevailed at the time of the incident. The scheduled domestic passenger flight was being operated under the provisions of Title 14 CFR Part 121 on an instrument flight rules flight plan. The captain, first officer, 9 cabin crew and 173 passengers were uninjured. The flight had departed the gate at 1030 and was en route to Chicago, Illinois. According to the Pilot/Operator Aircraft Incident Report Form 6120.1/2, the airplane was parked at the remote deicing pad 3W. Type 4 deicing fluid was being applied to the right rear quadrant and the right wing of the airplane using a deicing truck with boom. The deicing truck was moving in the area of the right wing trailing edge, forward toward the wingtip. The truck's boom was raised at the time. The driver maneuvered the vehicle too close to the right wing trailing edge at the aileron resulting in the mid-section of the boom coming in contact with the wing. The right aileron was crushed forward, wrinkled and torn. The airplane returned to the gate where passengers were deplaned uneventfully. The boom on the de-icing truck sustained scratched paint and a small crease in the sheet metal covering. An operational inspection of the truck revealed no anomalies. According to the written statements from the boom operator and deicing truck driver, the boom operator cleared the wing for movement when she was not actually clear. The United Airlines incident report stated that due to falling snow, visibility was poor. The closest official weather observation station was DEN which was located 2 nautical miles east of the occurrence site. The elevation of the weather observation station was 5,431 feet mean sea level. The routine aviation weather report (METAR) for DEN, issued at 1117, reported, wind, 100 degrees at 6 knots; visibility, 1/2 statute miles..., light snow, mist; sky condition, few 700 feet above ground level (agl), overcast, 1,800 feet agl; temperature minus 2 degrees Celsius (C); dewpoint, minus 03 degrees C; altimeter 29.86 inches; remarks, surface visibility 3/4.