The flight departed Washington National Airport, at 00:07 for a flight to Seattle. The flight stopped at Cleveland for fuel and oil and arrived at Chicago at 07:35. Shortly after takeoff at Chicago, the flight returned owing to rough operation of the left engine. The left magneto of this engine was replaced by a spare carried on the aircraft and the flight again departed at 12:15 for Minneapolis, made a fuel stop there, and arrived at Fargo at 16:40. One of the engines was spitting and coughing, but it would take a mechanic 15 minutes to get to the plane, and the crew decided to continue. The left engine started with some difficulty and the flight departed Fargo at 17:48 and made fuel stops at Billings and Felts Field, Spokane. The flight departed Spokane at 00:35 the next day on an IFR flight plan. At 02:07 the pilot of the DC-3 reported an engine failure to Seattle Center. Seven minutes later, Seattle Approach Control heard the pilot report that he was icing up and losing altitude. The flight was cleared for an approach to Boeing Field. The last transmission from the aircraft was received at 02:22, reporting that the flight was at 4,800 feet. The airplane struck 150-200 foot trees at the 3,500-foot level of Cedar Mountain while descending with wings level. The right wing tip was the first portion of structure to contact the trees, and both wing panels were progressively torn away to the center section in a series of decelerations. The fuselage broke into three sections, and the nose section was demolished. Some sources report that this airplane (msn 20432) was rebuilt as N3935C and sold to Canada as CF-DME in 1956. This however seems highly unlikely. PROBABLE CAUSE: “The progressive failure of both engines, due to the lack of compliance with proper maintenance standards.”