June 19, 1966
Nha Trang Air Base, Khanh Hoa Province, South Vietnam

Aerial view of Nha Trang, 1962 — the coastal city and air base where the June 1966 mass electromagnetic blackout occurred, cutting power to every generator, vehicle, and aircraft on the installation simultaneously. — U.S. Army / Wikimedia Commons (public domain)
Craft morphology
No NHI encounter documented for this event.