The Douglas DC-6 is a piston-powered airliner and transport aircraft built by the Douglas Aircraft Company from 1946 to 1958. Originally intended as a military transport near the end of World War II, it was reworked after the war to compete with the Lockheed Constellation in the long-range commercial transport market. More than 700 were built and many still fly today in cargo, military and wildfire control roles. The DC-6 was known as the C-118 Liftmaster in United States Air Force service and as the R6D Liftmaster in United States Navy service prior to 18 September 1962, after which all U.S. Navy variants were also designated as the C-118 under the 1962 United States Tri-Service aircraft designation system. Notable accidents and incidents Like every other major type in long service and operation, accidents and incidents have been recorded that have substantially reduced the numbers flying. The following list is typical of such a record of operational use. 1940s October 24, 1947 United Airlines Flight 608 crashed near Bryce Canyon, Utah while attempting an emergency landing after an inflight fire broke out, killing all 52 on board. June 17, 1948 United Airlines Flight 624 crashed near Aristes, Pennsylvania after a false fire alarm. All 43 on board were killed. July 4, 1948 An SAS DC-6 collided in mid-air with RAF Avro York MW248 over Northwood, London, killing all 39 on board both aircraft. November 29, 1949 American Airlines Flight 157 crashed while attempting a three-engine landing at Love Field; 28 of 46 people were killed. 1950s June 30, 1951 United Airlines Flight 610 struck the side of Crystal Mountain, Colorado after the crew deviated from the flight path for reasons unknown, killing all 50 passengers and crew on board. August 24, 1951 United Airlines Flight 615 crashed into Tolman Peak and into Dry Gulch Canyon below, southeast of Oakland, California; all 44 passengers and six crew were killed. February 11, 1952 National Airlines Flight 101 (a DC-6, N90891) crashed at Newark International Airport after a propeller reversed in flight, killing 29 of 63 on board and four on the ground. March 22, 1952 KLM Flight 592, a DC-6 (PH-TPJ, Koningin Juliana), crashed in a forest 7 mi northeast of Frankfurt International Airport, killing 45 of 47 on board. June 28, 1952 American Airlines Flight 910 collided in mid-air with a private single-engine Temco Swift on final approach to Dallas Love Field;