From flying saucers to UAP - how the U.S. government changed what it calls unexplained aerial sightings, and why the language shift matters for science and policy.
The public conversation about unexplained aerial sightings has long been dominated by a single acronym: UFO - Unidentified Flying Object. But over the past decade, the U.S. government quietly retired that label in official documents, replacing it with UAP. Understanding that shift is not merely semantic. It reflects a deliberate change in how government agencies frame the problem, what kinds of phenomena they are willing to investigate, and what level of scientific seriousness they are prepared to bring to the subject.
The term “UFO” entered American military vocabulary in the early 1950s, formalised during the era of Project Blue Book - the U.S. Air Force’s investigation that ran from 1952 to 1969. The acronym was descriptive but also baggage-laden. Decades of pop culture association with alien spacecraft made “UFO” a liability for any official or scientist who wanted to be taken seriously. Reports from military pilots were sometimes dismissed or discouraged because of that stigma.
The phrase “Unidentified Aerial Phenomena” appears in government records as far back as the late 1960s, but it was the 2020 establishment of the Unidentified Aerial Phenomena Task Force (UAPTF) that brought UAP into mainstream usage. Two years later, Congress took it further. The National Defense Authorization Acts for Fiscal Years 2022 and 2023 codified the broader term “Unidentified Anomalous Phenomena” - and the acronym UAP stuck to the new meaning.
The word “anomalous” in the current official definition is significant. AARO - the All-domain Anomaly Resolution Office, established by the Department of Defense on July 20, 2022 - defines UAP as sources of anomalous detections in one or more domains (airborne, seaborne, spaceborne, and transmedium) that are not yet attributable to known actors and that demonstrate behaviors not readily understood by sensors or observers.
That definition does several things at once. First, it removes the assumption that the object must be “flying” in any conventional sense. A submerged object, a signal anomaly on radar, or something transiting between sea and air can all fall within scope. Second, “anomalous” foregrounds the idea that the unexplained aspect is the observation itself, not necessarily an exotic craft. Sensor artifacts, atmospheric optics, and misidentified conventional objects are all legitimate candidate explanations under this framing.
A term that sometimes appears alongside UAP is UAS - Unidentified Aerial Systems, or sometimes Unmanned Aerial Systems (also UAS). The latter refers to remotely piloted vehicles, whether commercial drones or military assets. When the government refers to incursions near sensitive installations by UAS, it typically means drones operated by a known or suspected human actor - a security concern, but a different investigative problem from a genuinely unattributed UAP. The distinction matters because the Pentagon’s reporting infrastructure treats them differently, though in practice the initial sensor signature of a drone and a poorly understood aerial object can look similar.
AARO serves as the primary U.S. government body for detecting, identifying, and mitigating UAP. Its mission, established under 50 U.S.C. § 3373, is to minimise technological and intelligence surprise by resolving anomalous observations. According to the office’s FY 2024 annual report, AARO received 757 UAP reports during a single 13-month reporting period. Of the cases resolved during that period, the office determined that all resolved examples corresponded to prosaic objects - balloons, birds, and commercial drones.
That result is, itself, informative. The vast majority of reported UAP have conventional explanations once adequate data is gathered. AARO explicitly states it has “discovered no evidence of extraterrestrial beings, activity or technology” in its reviewed caseload. What the office acknowledges is that a small residue of cases lacks sufficient data for resolution - and that producing better sensor data is the appropriate next step, not premature conclusions.
Precise language shapes what questions get asked. “UFO” implies an object, implies flight, and implies the unknown is primarily about identity. “UAP” is deliberately broader - it encompasses the possibility that what observers are reporting may not be a solid object at all, and it situates the investigation within a multi-domain sensor framework rather than eyewitness tradition alone.
For journalists, researchers, and the public, the practical implication is straightforward: when reading government documents or congressional testimony, UAP and UFO are often used interchangeably in informal speech, but in formal policy contexts UAP carries the specific statutory meaning enshrined in the NDAA. The shift is not cosmetic. It is an attempt - still imperfect and ongoing - to bring anomalous observation reports into a framework where they can be evaluated with the same rigor applied to any other intelligence or scientific data problem.
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