The Short Version
Military pilots have reported encountering unidentified objects with extraordinary flight characteristics, but none have confirmed these are alien spacecraft. The most prominent pilot witnesses — Fravor, Graves, and Dietrich — described anomalous phenomena without claiming extraterrestrial origin. The strongest "alien craft" assertions come from David Grusch, a former intelligence officer (not a pilot), whose claims are secondhand and self-admittedly unproven. The Pentagon's AARO has explicitly stated no investigation has confirmed any UAP as extraterrestrial technology.