Project Blue Book Case #1310. On June 19, 1952, a bright object was observed over Yuma, Arizona — home to the Yuma Proving Ground, the U.S. Army's primary weapons testing facility for arid and desert environments. Yuma's year-round clear skies and flat desert terrain made it ideal for weapons testing, and the proving ground's vast restricted airspace was among the most closely monitored in the country.
Yuma also hosted the Marine Corps Air Station Yuma, where Marine aviators trained in the desert conditions similar to those they might encounter in combat. The combination of Army testing and Marine Corps aviation made Yuma's airspace extraordinarily busy with military traffic — yet also extraordinarily well-documented.
June 1952 was in the buildup to the July wave. The desert Southwest was contributing a steady stream of cases from the corridor connecting Yuma, Tucson, El Paso, and White Sands — a region where some of the most advanced weapons in the world were being developed and tested.
The object over Yuma did not match any test flight, weapons launch, or training mission scheduled at the proving ground or MCAS Yuma. Its brightness in the clear desert air was notable, and its behavior was inconsistent with any known aircraft type.
The case was classified "Unknown" — another entry from the heavily militarized desert Southwest.