What's the difference between a UFO and a UAP?

“UFO is the legacy 1950s term ('Unidentified Flying Object'); UAP is the current U.S. government term ('Unidentified Anomalous Phenomena') and includes underwater and trans-medium objects.”

UFO and UAP refer to the same broad category — sightings that resist conventional identification — but the terms have different scope and provenance. UFO ("Unidentified Flying Object") was coined by the U.S. Air Force in 1953 and is air-only by definition. UAP originally stood for "Unidentified Aerial Phenomena" and was adopted by the Navy in 2019 to remove the cultural baggage attached to UFO. In 2022 Congress expanded the acronym to "Unidentified Anomalous Phenomena" to cover trans-medium objects observed in air, in space, on the surface of the ocean, and underwater. UAP is the term used in 50 U.S.C. § 3373, in all AARO publications, and across all 162 files in PURSUE Release 01. UFO remains common in journalism and popular culture; both terms describe the same phenomena.