Fort Monmouth, New Jersey UFO Sighting (11 September 1951) — FBI Files
A first saucer wave case from Fort Monmouth, New Jersey. Two SCR 584 radar sets picked up the same target northeast of Fort Monmouth at an elevation of approximately 31,000 feet.
Background
On 11 September 1951, in Fort Monmouth, New Jersey, U.S. government investigators recorded an unidentified-object incident later released to the public on May 8, 2026 as part of the Presidential Unsealing and Reporting System for UAP Encounters (PURSUE). The incident is one of the first wave of “flying saucer” reports that swept the United States after the Kenneth Arnold sighting of June 1947 and the Roswell incident of July 1947. The case was filed with the Federal Bureau of Investigation, whose Knoxville, Albuquerque, Los Angeles, and other field offices routed UFO reports to headquarters under the Bureau’s standing protocols for the protection of vital installations.
What the document records
Two SCR 584 radar sets picked up the same target northeast of Fort Monmouth at an elevation of approximately 31,000 feet. The radar sets were unable to track the target’s range due to its speed, requiring manual tracking. The target’s speed exceeded the radar’s aided tracking ability, and its echo signal fluctuated with its maneuvers.
The number of witnesses is not specified in the released document.
Type of case
The case is principally a radar track, with the unidentified object being detected on military or civilian radar equipment.
Status
All records released under the PURSUE program are designated unresolved by the All-domain Anomaly Resolution Office (AARO) by default. The federal government has not concluded that the events were anomalous, has not concluded that they were conventional, and has not ruled out either possibility. Conventional candidates for sightings of this period include experimental aircraft, weather balloons (especially the Project Mogul series in the late 1940s), atmospheric optical phenomena such as sundogs and lenticular clouds, and astronomical objects including Venus, the Moon, and meteors near the horizon.