United Airlines Flight 624, a Douglas DC-6, crashes near Mount Carmel, Pennsylvania, killing all 43 people on board.

United Air Lines Flight 624 was a scheduled domestic passenger flight from San Diego, California, to New York City, with stopovers in Los Angeles and Chicago. The four-engined, propeller-driven Douglas DC-6 crashed at 1:41 pm Eastern Daylight Time on June 17, 1948, outside Aristes, Pennsylvania, resulting in the deaths of all 4 crew members and 39 passengers on board. The crew had deployed the aircraft's CO₂-based fire extinguisher system, without opening the pressure relief valves designed to ventilate CO₂ out of the cabin. The part-incapacitated crew then began an emergency descent and subsequently crashed into a hillside.

The Douglas DC-6 is a piston-powered airliner and cargo aircraft built by the Douglas Aircraft Company from 1946 to 1958. Originally intended as a military transport near the end of World War II, Douglas reworked it after the war to compete with the Lockheed Constellation in the long-range commercial transport market. Douglas built over 700, and many still fly in cargo, military, and wildfire control roles.

Mount Carmel is a borough in Northumberland County, located in the Coal Heritage Region of Central Pennsylvania's Susquehanna River Valley, United States. The population was 5,725 at the 2020 census. It is located 88 miles (141 km) northwest of Philadelphia and 71 miles (114 km) northeast of Harrisburg, in the Coal Region. It is completely encircled by Mount Carmel Township.