Flex Mentallo

Psychological reasons

Hoaxes

Moon dogs

Fata Morgana

Mirages

Clouds

Weather balloons

Aircraft

Among the most commonly found identified sources of UFO reports are: Meteors

In the Pacific and European theatres during World War II, "foo-fighters" (metallic spheres, balls of light and other shapes that followed aircraft) were reported and on occasion photographed by Allied and Axis pilots. Some proposed Allied explanations at the time included St. Elmo's fire, the planet Venus, hallucinations from oxygen deprivation, or German secret weapons.

On August 5, 1926, while travelling in the Humboldt Mountains of Tibet's Kokonor region, Russian explorer and artist Nicholas Roerich (whose work is mentioned by Lovecraft in At the Mountains of Madness) reported, members of his expedition saw "something big and shiny reflecting the sun, like a huge oval moving at great speed. Crossing our camp the thing changed in its direction from south to southwest. And we saw how it disappeared in the intense blue sky. We even had time to take our field glasses and saw quite distinctly an oval form with shiny surface, one side of which was brilliant from the sun." Another description by Roerich was of a "shiny body flying from north to south. Field glasses are at hand. It is a huge body. One side glows in the sun. It is oval in shape. Then it somehow turns in another direction and disappears in the southwest."

According to records released on August 5, 2010, British wartime prime minister Winston Churchill banned the reporting for 50 years of an alleged UFO incident because of fears it could create mass panic. Reports given to Churchill asserted that the incident involved an Royal Air Force (RAF) reconnaissance plane returning from a mission in France or Germany toward the end of the Second World War. It was over or near the English coastline when a strange metallic object that matched the aircraft’s course and speed for a time before accelerating away allegedly intercepted it before disappearing. The plane's crew were reported to have photographed the object, which they said had "hovered noiselessly" near the aircraft, before moving off.

On February 28, 1904, there was a sighting by three crewmembers on the USS Supply 300 miles (483 km) west of San Francisco, reported by Lieutenant Frank Schofield, later to become Commander-in-Chief of the Pacific Battle Fleet. Schofield wrote of three bright red egg-shaped and circular objects flying in echelon formation that approached beneath the cloud layer, then changed course and "soared" above the clouds, departing directly away from the earth after two to three minutes. The largest had an apparent size of about six Suns, he said.

In April 1897 thousands of people reported seeing "airships" in various parts of the United States. Many signed affidavits. Scores of people even reported talking to the pilots.

UFO'S have been reported throughout history. They were seen as omens, angels, or miracles.

Project Sign eventually evolved into Project Grudge, and then the better-known Project Blue Book. Captain Edward J. Ruppelt, who headed Project Blue Book, coined the acronym “UFO”.

This resulted in the formation of Project Sign at the end of 1947, the first publicly acknowledged USAF UFO investigation.

Three weeks later they came to the conclusion that the saucer reports were not imaginary or adequately explained by natural phenomena.

On July 9th Army Airforce Intelligence began an investigation of the sightings - mostly from pilots and military personnel - with the help of the FBI.

Ted Bloecher collected reports of 853 flying disc sightings that year from 140 newspapers from Canada and every U.S. state save Montana.

Dahl claimed he was later approached by a man in a dark suit and told not to talk about the incident. The story was later retold in Gray Barker's book "They Knew Too Much About Flying Saucers," which helped to popularize the image of "men in black" in mainstream culture.

Fred Crisman and Harold Dahl were harbor patrolmen on a workboat who saw six doughnut shaped objects in the sky near Maury Island in Puget Sound in June 1947. According to Crisman and Dahl, one of the objects dropped a substance that resembled lava or "white metal" onto their boat, breaking a worker's arm and killing a dog.

In February 1980, the National Enquirer ran an interview with Major Jesse Marcel, who had expressed his belief that the military covered up the recovery of an alien spacecraft. The article brought the Roswell incident to world wide attention.

It was not until many years later that claims were made of an alleged cover-up.

The U.S. government attributed the crash to a secret U.S. military Air Force surveillance balloon.