What happened
On the morning of the accident, United Airlines Flight 736, a DC-7, departed Los Angeles International Airport for New York. The flight was carrying 42 passengers and 5 crew members. Following an IFR flight plan via Ontario and Denver, the aircraft climbed through 12,000 feet and eventually reached its assigned cruising altitude of 21,000 feet. The last position report from the commercial flight indicated it was over Daggett and expected to reach the Las Vegas omni range station by 0831.
Simultaneously, an F-100F, registration 56-3755, departed Nellis Air Force Base in Las Vegas for a VFR instrument training mission. The aircraft was occupied by an instructor and a trainee pilot. At approximately 0823, the military crew requested an altitude assignment to perform a simulated ADF instrument jet penetration using the KRAM radio station as a reference. The controller assigned the aircraft 28,000 feet. After reporting they were over the station and beginning their descent from 28,000 feet, no further updates were received.
At 0830, an emergency transmission was intercepted by Aeronautical Radio offices in Los Angeles, Denver, and Salt Lake City, in which United 736 reported a midair collision over Las Vegas. Concurrently, an unrecorded distress call from the F-100F was heard by controllers and other pilots, stating "Mayday, Mayday" followed by a report of either a flameout or an ejection. The collision occurred at 21,000 feet, approximately 9 miles southwest of the Las Vegas VOR station. Both aircraft fell out of control, resulting in 47 fatalities on the commercial airliner and the death of both pilots in the fighter jet.
Findings
Investigations into the accident identified that the collision was driven by a high rate of near head-on closure at high altitude. Contributing factors included human and cockpit limitations, as well as a failure by Nellis Air Force Base and the Civil Aeronautics Administration to implement necessary measures to mitigate known risks of collision exposure.