The aircraft operating the service, a Douglas DC-4 propliner, registered as N30062,[1] crashed into Medicine Bow Peak, near Laramie, Wyoming, on October 6, 1955, killing all 66 people on board (63 passengers, 3 crew members).

[2][3] Another 66 lives had been lost earlier that year in the March 22 crash in Hawaii of a United States Navy Douglas R6D-1 Liftmaster military transport aircraft,[4] and 66 had also died in the mid-air collision of two United States Air Force C-119G Flying Boxcars over West Germany (1955 Altensteig mid-air collision) on August 11, placing the three crashes in a three-way tie as the deadliest aviation incidents in 1955.

[7] An expected position report from the United crew, scheduled for 8:11 a.m. while over Rock River, was not received, and repeated attempts to make radio contact with flight 409 were met with no response.

After a search of Elk Mountain failed to find the missing DC-4, Conine and his observer spotted at 11:40 a.m. a black stain and wreckage just southwest of the highest portion of Medicine Bow Peak.

Only a tail piece, part of the fuselage and a wing of the plane had been located at mid-afternoon by rescuers who fought snowdrifts and a howling wind on the 12,005-foot Medicine Bow Peak.

At the base of the almost perpendicular cliff where the aircraft hit, movement was hindered by a wide talus of weathered, fragmented rock and large boulders, all piled loosely on a steep slope.

Due to safety concerns, the CAB accident investigation team —not trained in alpine mountaineering techniques— was unable to visit the cliff location where the DC-4 initially hit.

[9] Regardless of the disposal method, small fragments of flight 409's airframe and parts of the engines still exist in the area surrounding the crash site.

[3] [note 1] The 66 lives lost on Medicine Bow Peak remained the highest death toll on a scheduled airline flight in the U.S. for less than a year.

[12] On August 25, 2001, a privately funded bronze memorial plaque was dedicated in the Miner's Camp turnout (41°20′30″N 106°18′21″W / 41.34153°N 106.30586°W / 41.34153; -106.30586), along Wyoming Highway 130 (Snowy Range Road).