Unidentified anomalous phenomena, or UAP, are observations that cannot be identified at the time of reporting as known aircraft, spacecraft, natural effects, or other familiar objects. The term grew out of the older UFO vocabulary and was broadened in U.S. law to cover incidents in multiple domains, including apparent transitions between them. “Unidentified” describes the state of the information, not the origin of whatever was observed.

Reports range from a single light seen briefly to encounters recorded by pilots, radar, infrared cameras, or several systems at once. That variety is why UAP sightings cannot be treated as one uniform phenomenon. Balloons, birds, drones, satellites, astronomical objects, sensor artifacts, and incomplete recollections account for many cases. A smaller residue remains unresolved, often because the available imagery lacks range, calibration, weather, platform position, or other metadata needed to reconstruct motion and size.

Government attention has also changed form. The Air Force’s Project Blue Book cataloged reports during the Cold War; today the All-domain Anomaly Resolution Office receives military and federal reporting, analyzes cases, and publishes imagery and annual assessments. NASA’s 2023 independent study did not attempt to identify past cases. It instead recommended standardized reporting, better calibrated observations, and use of civilian data so that future cases arrive with more scientific value.

The modern UAP issue therefore joins aviation safety, intelligence collection, scientific uncertainty, and public demands for UAP disclosure. Official acknowledgment that a report is unresolved is meaningful, but it is not confirmation of non-human intelligence. The central development since 2017 is institutional: unusual observations once handled inconsistently now have reporting channels, statutory definitions, congressional oversight, and a growing public record against which competing explanations can be tested.