United Airlines Flight 521, a Douglas DC-4, was a scheduled flight departing from LaGuardia Airport to Cleveland, Ohio on May 29, 1947. While attempting to take off from runway 18, the aircraft failed to get airborne, overran the end of the runway, ripped through an airport fence onto traffic on the Grand Central Parkway, and slammed into an embankment, ultimately plunging into a pond and exploding. Ten people escaped the flaming wreckage; only six of those survived.
It was the worst commercial aviation disaster in United States history at the time. This record stood for less than 24 hours when an Eastern Airlines DC-4 crashed near Baltimore, Maryland killing all 54 aboard.