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.

Attempts were made to accomplish this, but despite the use of explosives, artillery fire and —according to most sources— napalm bombs dropped from aircraft, complete obliteration of the wreckage was not possible.

[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).