Los Alamos Green Fireballs — Nuclear Site Overflights

Beginning in December 1948, a series of green fireballs began appearing over the Los Alamos and Sandia national laboratories — the United States' primary nuclear weapons development sites. Unlike meteors, the objects flew horizontal flight paths, did not produce sonic booms, and appeared at low altitude with controlled trajectories. The Air Force convened Project Twinkle specifically to instrument and document the phenomenon. Dr. Lincoln La Paz, a world-renowned meteor expert at the University of New Mexico, was contracted by the FBI to analyze the sightings. La Paz concluded in a classified report that the objects' behavior was inconsistent with any natural phenomenon, including meteors, ball lightning, and atmospheric electricity. He formally assessed them as artificial objects of undetermined origin. The FBI opened a national security investigation given the proximity to nuclear facilities. Declassified FBI files show Air Force intelligence was acutely concerned about the strategic implications of unknown craft conducting repeated overflights of the most sensitive nuclear sites in the United States.