Nocturnal Light (NL)

Nocturnal Light, abbreviated NL, is J. Allen Hynek's classification for an unexplained light seen moving or hovering in the night sky — no daytime structure, no landing, no occupant, just an anomalous point or glow of light. It is both the single most common UFO report type on file anywhere in the world and, by Hynek's own admission, the least evidential: a distant light at night gives an observer almost nothing to judge distance, size, or speed against, which is precisely why NL reports are the category most inflated by mundane sources — Venus and other bright planets, satellites (especially Starlink launch trains since 2019), aircraft landing lights, and Chinese lanterns. The Phoenix Lights of March 1997 illustrate the category's split personality: thousands of Arizona witnesses reported a mysterious V-formation of lights early that night (still officially unresolved to most investigators' satisfaction), while a separate, later set of stationary lights over the same city was conclusively traced to flares dropped by Air National Guard aircraft. That split — one NL episode genuinely puzzling, another explained the same evening — is why serious ufologists treat NL reports as the weakest tier of evidence even while acknowledging that a small residue resists every conventional explanation offered.