Acceso Oeste lights

Official source account — 2015 annual report, printed page 12: A witness photographed slowly moving lights over Acceso Oeste, Buenos Aires Province, on 28 July 2015 and reported an accompanying sound. CEFAE concluded that the lights were compatible with the nighttime navigation lights of one helicopter, showing its left side as it moved from north toward west. The report notes that changing viewing geometry can change the apparent triangle formed by the lights, and compares the sound with that of a piston-powered helicopter. The summaries distinguish reported observations from the agency’s proposed explanations. Source Type A/B ratings describe explanatory confidence and are not encounter classes.