On January 31, 2001, about 1315 Alaska standard time, a Douglas DC-6B airplane, N4390F, sustained substantial damage during landing at the Donlin Creek Airstrip, a remote mine site located about 12 miles north of Crooked Creek, Alaska. The airplane was being operated as a visual flight rules (VFR) cargo flight under Title 14, CFR Part 125, when the accident occurred. The airplane was registered to and operated by Everts Air Fuel, Inc., Fairbanks, Alaska. The two certificated airline transport pilots, and the flight engineer, were not injured. Visual meteorological conditions prevailed, and a visual flight rules (VFR) flight plan was in effect. The flight originated at the Fairbanks International Airport, Fairbanks, about 1130. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on February 2, the captain related that the purpose of the flight was to deliver about 4,800 gallons of fuel oil to the remote mining site. He said that the 5,400 feet long by 100 feet wide airstrip was situated within hilly, snow-covered terrain. He added that the airstrip has a 7 percent uphill grade. Flat light conditions existed at the airstrip, and light snow showers were present, with visibility reported at 2 miles. The captain stated that during final approach, as the airplane passed over the airstrip threshold, flat light conditions made it very difficult to discern where the airstrip surface was. He said that the initial touch down was "firm", but was thought to be within acceptable tolerances. Just after touchdown, the left wing broke free from the airplane at the wing to fuselage attach point. The airplane veered to the left, and off the left side of the runway. The captain said that the airplane's computed landing weight was 92,260 pounds.