On June 25, 2021, the Office of the Director of National Intelligence released a nine-page unclassified Preliminary Assessment on Unidentified Aerial Phenomena covering 144 UAP incidents reported by U.S. military personnel between 2004 and 2021, concluding that 143 of those cases remained unexplained.

The assessment identified five possible explanatory categories: airborne clutter, natural atmospheric phenomena, U.S. government programs, foreign adversary systems, and 'other.' It documented 18 cases with unusual flight characteristics, including stationary hovering in strong winds and abrupt maneuvering, and 11 near-miss collision reports. The report stated UAP 'clearly pose a safety of flight issue and may pose a challenge to U.S. national security.'