Project Blue Book Case #2840. On December 24, 1953, witnesses in El Cajon, California — a community in the valley east of San Diego — observed a bright object in the Christmas Eve sky. El Cajon's position in the San Diego metropolitan area placed it within one of the most militarily significant regions on the West Coast.
San Diego in 1953 was the Navy's primary Pacific Fleet base. Naval Air Station North Island, the Marine Corps Recruit Depot, and numerous other installations ringed the bay. Convair's massive aircraft plant — producing the B-36 Peacemaker bomber and the Atlas ICBM — dominated the waterfront. El Cajon sat east of this complex, in a valley that served as an approach corridor for military and civilian aircraft.
The Christmas Eve timing gave the case an unusual character, as many witnesses were likely outdoors for holiday activities. The object's brightness was described as significantly exceeding celestial objects or aircraft lights.
The San Diego area's dense military airspace was well-documented, and no aircraft matched the sighting. The case was classified "Unknown."