Extraterrestrial Abduction Day: Five unexplained cases that have left the experts searching for answers

We decided it's time to take a look at the most mysterious, disturbing and confusingly terrifying accounts of UFO sightings and abduction.

So let's get started...

Frederick Valentich: 'It's not an aircraft'

The disappearance of Frederick Valentich took place on Saturday, October 21 1978.

The 22-year-old was flying a Cessna 182L light aircraft over Bass Strait in Australia during a 125-mile training flight when he got in touch with Melbourne air traffic control.

He told them that 300 metres above him was another aircraft.

However, his chilling final words before cutting out were: "It's not an aircraft."

And to add to the mystery, Valentich's disappearance coincided with several UFO sighting reports on the same day of the incident.

Getty Heartbroken: Guido Valentich holds a photograph of his son Frederick, a pilot who went missing three days earlier whilst on a flight from Melbourne to King Island in 1978

Valentich was an experienced pilot. He was studying to became a commercial pilot, and at the time had 150 hours flying time, holding a class-four ranking which allowed him to fly whenever he wanted.

In the years that followed, his father revealed that his son had spent many years living in fear of UFOs and was an adamant believer in their existence.

After his immediate disappearance, a sea and air search was conducted. However after a 1,000 square-mile patrol, the efforts were stopped on October 25, 1978.

Australian government officials have since brushed off any suggestion of extraterrestrial involvement in his dissappearance.

One official was quoted saying: "Valentich became disorientated and saw his own lights reflected in the water, or lights from a nearby island, while flying upside down."

Getty It's a mystery: The pilot's body was never found

Other theories since the incident suggest that he faked his own death, but he remains an iconic figure among die-hard UFOlogists.

What's the truth? We'll let you decide...

Travis Walton: 'Few abduction reports have generated as much controversy'

In February 1975, Travis Walton was working with a logging crew in the Apache-Sitgreaves National Forest in Arizona alongside Ken Peterson, John Goulette, Steve Pierce, Allen Dallis and Dwayne Smith.

On their way back from work one night, the men claim to have seen a shining yellow light in the sky.

Shortly afterwards, a "golden disc" which they described as a "glowing, metallic" object was spotted in the air.

Open Minds Production/youtube Speaking: Travis Walton went missing for days after the bizarre incident

Travis, against the wishes of the other men, sprinted towards it. The men claim that beams of blue and green light then struck the logger, who was then hurled through the air.

In a panicked frenzy, his pals in the pickup truck made off.

Writing about the case, Jerome Clark, a UFO historian, wrote that "few abduction reports have generated as much controversy".

Even though they were worried that no one would believe them, the men returned home and called the police

Later they returned to the forest with 50 officers to try and find Travis, but there was no trace.

After four days, the search party gave up. Travis claims that when he woke up, he thought he was in a hospital.

But he then realised that there were creatures who were four-feet tall with "huge eyes" standing over him.

They then put a mask over his face, and when he woke up he found himself 30 miles away from where he initially dissappared.

Travis stumbled to the nearest town, where he reached a payphone. He managed to call his family, and let them know he was safe.

He thought it was the same night that he went missing, but it had in fact been five days.

The incident sparked an international sensation, with media speculation accusing Travis that he was hallucinating on drugs.

Speaking of the incident years later, Travis said: "I like to think I was in the wrong place at the wrong time, and I did the wrong thing, getting too close.

"I don't know where they come from, and who they were.

"To me, they're still a mystery."

Betty and Barney Hill: 'They put me on a table, and said they wanted to check my nervous system'

Another tale of UFO abduction is that of Betty and Barney Hill.

The couple, from New Hampshire, claim that they were abducted by aliens on September 19, 1961, while making their way back home from a holiday in Niagara Falls and Montreal.

Betty claimed that she saw a bright light in the sky - initially thinking it was just a shooting star.

However they saw it grow bigger and bigger, and Betty convinced Barney to stop the car so she could get out and take a look.

Wikipedia Abducted: Barney and Betty Hill, who claim they were abducted

Taking their dog along for a walk, the couple got out of the vehicle and Betty looked through binoculars to see an "odd-shaped" object in the sky.

They got back into the car and kept driving, however eventually they claim a UFO moved above their vehicle.

That's when the couple felt strong vibrations and heard strange buzzing sounds.

All of a sudden, they found themselves 35 miles away from where they had been initially - but their memory was fragmented.

In the days that followed the couple conducted a six-hour interview with the National Investigations Committee On Aerial Phenomena.

Under hypnosis the couple said they were subjected to medical experiments, with various specimen taken from them.

Six months later, again under hypnosis, Betty managed to draw a star map detailing where "The Leader" of the craft said the aliens had come from.

Some experts have even speculated what star system her map may show.

Betty, who died in 2004, previously said of her abduction: "I was taken on board. Barney was taken into one room and I was taken into another. The one who did the testing we called The Examiner.

"First they put me on a stool and they checked my eyes, ears, nose, throat. They put me on a table, and said they wanted to check my nervous system.

"Then they tried to insert a needle-like instrument in my navel which caused pain so they stopped doing it. Barney’s exam was very much like mine in the beginning except they were interested in his bone structure."

John Salter Jr: But not all alien abductions are cruel.. .

We'll end on a positive note, because John Salter Jr has a rather different take on an alien abduction.

The sociology professor was driving through Wisconsin towards Mississippi with his son in 1988 when he had an encounter with "friendly" aliens.

He claims they were all of a sudden gripped by amnesia, finding themselves abducted but not remembering how.

Joel Marcelo/youtube John Salter Jr: His encounter with aliens came while he was driving with his son

After regaining consciousness, the pair saw short, humanoid figures and they were led away to be experimented on.

But this wasn't a problem for Mr Salter.

He and his son were led towards a bright room where tubes were inserted into their nostrils for experimentation which was described as being "ethical and honourably done to good ends".

Mr Salter even said that he felt positive health benefits after the incident.

Speaking of the abduction, he said: "My immunity is heightened. Cuts and scratches now clot immediately and heal rapidly.

"My head hair, fingernails and toenails are growing two to three times the normal rate.

"Some of my age spots have disappeared. And the wrinkles in my face have faded."