1945 – 1949: UFO|UAP | Entity Sightings by Date Hub

The period between 1945 and 1949 is recognized as the foundational era of the modern UFO phenomenon, transitioning from wartime anomalies to a global cultural obsession and formal military study. Following the “foo fighters” of World War II, this era saw the birth of the term “flying saucer” — coined after Kenneth Arnold’s June 1947 sighting near Mount Rainier — and the establishment of the first official U.S. government investigations into what was then considered a potential national security threat. By decade’s end, the phenomenon had grown from scattered wartime anomalies into a recurring feature of Cold War military life, with green fireball waves over New Mexico’s nuclear sites, recurring searchlight-illuminated sightings across the American Midwest, and the earliest contactee narratives all taking shape before 1950 arrived.

1945: UFO|UAP | Entity Sightings by Date

The tail end of the “foo fighter” era, as wartime aerial anomalies persisted into the war’s final year, not yet named or publicly framed as “flying saucers.”

1946: UFO|UAP | Entity Sightings by Date

A transitional year dominated by the Scandinavian “ghost rocket” wave, widely investigated at the time as a possible Soviet weapons test.

1947: UFO|UAP | Entity Sightings by Date

The phenomenon’s breakout year: Kenneth Arnold’s Mount Rainier sighting coins the term “flying saucer,” followed within days by the Roswell incident and a nationwide sighting wave.

1948: UFO|UAP | Entity Sightings by Date

The Air Force’s Project Sign takes shape, the Mantell incident becomes the first widely publicized fatality linked to a UFO pursuit, and the New Mexico green fireball wave begins.

1949: UFO|UAP | Entity Sightings by Date

Project Grudge replaces Project Sign with a debunking mandate as the green fireball wave intensifies around Los Alamos and Sandia, the Fort Hood, Texas wave unfolds, and the earliest contactee narratives (Daniel Fry) emerge at White Sands.

Official U.S. Government Investigations

Project Sign (1947-1949): The first official Air Force study, which initially considered “interplanetary” origins before being replaced.

Project Grudge (1949): Succeeded Project Sign with a focus on debunking sightings to alleviate public anxiety and “war hysteria.”

AARO Historical Review: A 2024 report found no evidence that these early cases represented extraterrestrial technology, instead attributing them to misidentifications of secret programs or natural phenomena.

Five years turned a handful of wartime anomalies into a permanent feature of American life: a name (“flying saucer”), a bureaucracy (Project Sign, then Grudge), and a body of cases — Roswell, Mantell, the green fireballs, Kenneth Arnold’s own sighting — that every subsequent decade of ufology would measure itself against. Whatever these objects were, the pattern of official study, official skepticism, and public fascination that defines the field to this day was set in these five years.

“They flew like a saucer would if you skipped it across the water.”

Kenneth Arnold, describing his June 24, 1947 Mount Rainier sighting — the account that gave the phenomenon its name.