What happened
On June 30, 1956, United Air Lines Flight 718, an L-1049, departed from Los Angeles International Airport for a scheduled service to Chicago. The aircraft took off from runway 25L at 0904, following a flight plan that included several waypoints such as Palm Springs and Needles. During the climb, the crew was instructed by air traffic control to maintain visual flight rules (VFR) conditions while ascending to an assigned altitude of 21,000 feet.
The aircraft proceeded through its planned route, providing regular position reports via company radio. At 0958, the crew reported being over Needles at 21,000 feet. However, at approximately 1031, an unintelligible radio transmission was intercepted by communication stations in Salt Lake City and San Francisco; subsequent playback revealed the crew of Flight 718 stating they were "going in." This coincided with a mid-air collision involving another aircraft.
Findings
Investigations into the accident determined that the mid-air collision was caused by the pilots' inability to visually identify and avoid each other in time. The investigation noted several contributing environmental and operational factors:
- Presence of overcast layers at 15,000 feet and cumulus clouds in the vicinity of the Grand Canyon.
- Potential pilot preoccupation with cockpit duties or passenger service.
- Limitations regarding human visual perception and cockpit visibility.
- A lack of air traffic advisory services in the uncontrolled airspace where the collision occurred.
There was no evidence to suggest that mechanical failure or any malfunction of the L-1049 contributed to the event.