island. Other facilities SFO is home to the one of the largest single aircraft maintenance bases in the world with complete MRO base operations (maintenance, repair, overhaul, painting, welding, machine shop, tool and die, parts manufacturing, fabrication, engineering, and retrofitting (Boeing and Airbus certified, among others)). It serves as the principal Global MRO Base for United Airlines and serves over 40 other airlines, military customers, and aircraft lease operators. The eastern side of the airfield is dominated by the Superbay, a maintenance hangar capable of holding four 747s. Originally constructed in the 1970s, the facility is shared by United Airlines and American Airlines. Nippon Cargo Airlines has its San Francisco branch on the airport property. Prior to its merger that formed AirWest, Pacific Air Lines had its corporate headquarters on the grounds of the airport. Hughes Airwest, the successor to Air West, also had its headquarters on the grounds of the airport. The United States Coast Guard operates Coast Guard Air Station San Francisco with its ramp and buildings near the cargo terminal, operating six MH-65 Dolphin helicopters. Accidents and incidents On February 9, 1937, a United Airlines Douglas DC-3A-197 transport liner circled the airport, then crashed into the bay, killing 11 people. On September 12, 1951, United Airlines Flight 7030 plunged into the bay during a training exercise killing all three crew members. On April 20, 1953, Western Airlines Flight 366, a Douglas DC-6 on a scheduled evening crossbay flight to Oakland International Airport, crashed three minutes after departing SFO into San Francisco Bay. There were eight fatalities (4 crew, 4 passengers) of the 10 occupants on board. On October 29, 1953, British Commonwealth Pacific Airlines flight 304, a Douglas DC-6 en route from Sydney, Australia, with fuel stops in Auckland, New Zealand, Fiji, and Honolulu, crashed on approach to SFO into Kings Mountain in San Mateo County. All 19 passengers and crew members died. On February 20, 1959, a Pan American DC-7C crashed and burned on the runway. The three crew members on board survived. On February 3, 1963, Slick Airways Flight 40 crashed and burned after striking approach lights on runway 28R, killing the four people on board. On December 24, 1964, Flying Tiger Line Flight 282, a Lockheed Constellation cargo aircraft departing for New York City, crashed in the hills west of the airport, killing all three crew members on board. On June 28, 1965, Pan