World UFO Day: Here are five of the most famous 'flying saucer' sightings

Unidentified Flying Objects (UFO) have captured people's imagination for thousands of years. There are myths and legends, stories and folklore all woven around the experience of sighting "something" in the sky.

Because it is merely "something"— a disk, a flash of light, an object the shape of nothing ever seen before— it is classified as a UFO. UFOs are more often than not associated with aliens, since legends have it that these flying objects are being flown by, again, "someone" or "something".

This mystery surrounding UFOs has endured since the time of the Mayans— when legend (and a film) have it that aliens contacted the civilization. And while UFO sightings are reported year-round, through decades and via centuries, there is a specific day dedicated for them: July 2.

In lieu of World UFO Day, let us take a look at the most famous sightings of flying objects rushing across the mysterious skies.

Kenneth Arnold sighting:

Two years after the end of World War II, in 1947, American aviator and businessman Kenneth Arnold reported seeing nine blue, glowing objects flying in a V-shaped formation while he was flying his aircraft near Mount Rainier, Washington.

Arnold described the motion of the craft as a "saucer if you keep it across water", which is where the term "flying saucer" for UFOs could have come from.

Roswell incident:

Strictly speaking, this is not exactly a UFO sighting, but it is infamous in the UFO lore for the conspiracy theories that it produced. This particular incident, in fact, happened sometime after the Arnold incident, in the same year.

What happened was that in the summer of 1947, William Brazel, a rancher, discovered debris in one of his New Mexico pastures. This wreckage had some inexplicable material, including metallic rods and chunks of plastic, among others. Brazel reported the wreckage, and soon, soldiers reportedly from the Roswell Army Air Force base nearby retrieved the material.

Ever since, exhaustive analyses on what really happened there have been doing the rounds, with many claiming it was UFO debris. It wasn't, per the Air Force, which came out with a report on the incident 50 years later. The wreckage was that of a crashed weather balloon, a part of Project Mogul, in which the Americans were trying to detect Soviet nuclear tests.

Billy Meier in India — and UFOs

Billy Meier is a UFO researcher. He claims that aliens contacted him for the first time at the age of five (his age, not the aliens'). Ever since, they have been in contact with Meier, according to him.

Meier, in fact, photographed UFOs over the skies of Delhi when he paid a visit to the national capital back in 1964.

The USS Nimitz UFO incident:

This could be one of the best documented UFO sightings in history. One afternoon in November 2004, two F/A-18F Super Hornet fighter jets from the USS Nimitz carrier were flying over Pacific Ocean when they detected unknown aerial objects.

These objects, according to reports, were flying at an unusual speed and had an unidentified shape. What's more, the incident was captured on videos, titled "GIMBAL.wmv," "GOFAST.wmv," and "FLIR.mp4". These videos were declassified by the Pentagon on April 28 this year and you can watch them here.

The Tehran incident:

Now, here is an incident in which you do not want a contact with the said UFO. In 1976 Tehran, residents started seeing a bright light in the sky, prompting the Iran Air Force to take to the skies to investigate.

According to reports, two F-4 jets were sent to investigate, and both complained of malfunction in their aircraft. The second pilot, in fact, said that the UFO released a glowing object aimed at him, which is when his fighter jet, too, began to malfunction, prompting him to return to base.

But this particular incident has explanations for everything "strange" reported, including a history of defective aircraft, meteor showers and the bright light being Jupiter.