Associated Press

For just over two weeks, the disappearance of Malaysia Airlines Flight 370 has captivated the news cycle. Theories about the whereabouts of the missing plane and its passengers have been in no short supply, but recent reports have concluded that the plane did indeed crash into the Indian Ocean. The question now is why.

As long as no piece of the plane has been found, the cause of the disappearance is likely to remain a mystery. We've compiled 10 other such mysteries that, unlike the Malaysian flight, have never been solved, and probably never will be.

Missed the boat
Wikimedia commons

The largest disappearance of a U.S. Navy ship occurred in March 1918, and to this day the remains of the USS Cyclops and its 306 crew members remains undiscovered.

Built just prior to World War I, the USS Cyclops had only been in commission for eight years when she disappeared. After leaving port in Barbados on March 4, heading for Baltimore, the USS Cyclops simply disappeared. Everything from bad weather to the Bermuda Triangle has been blamed for the vanishing act, but no matter what the cause, the fact that no wreckage or trace of the crew has ever been found has left the case of the USS Cyclops unsolved.

The Babushka Lady
Associated Press

Though the assassination of President John F. Kennedy has generated numerous amounts of questions concerning the authenticity of the official account, the Babushka Lady is one element that doesn’t even have an official explanation for skeptics to question.

A number of films and photographs documenting the Kennedy assassination depict what appears to be an elderly woman (wearing a headscarf typically worn by old Russian women, hence the media naming her Babushka, after the Russian word for grandmother) holding a camera while the assassination took place.

During the investigation, authorities attempted to track down the woman, but to no avail. She never came forward to testify of what she saw, nor did the film she likely shot ever surface. Though there have been numerous conspiracy theories about the identity of the Babushka Lady (and even someone who claimed to be her) none has stood the test of scrutiny. Her identity remains unknown to this day.

The Zodiac killer
Associated Press

Beginning in October of 1966, a string of brutal murders swept the nation’s newspapers and confounded law enforcement in northern California, where the murders were taking place.

With up to eight suspected victims, the Zodiac killer — whose name derives from a series of letters delivered to local newspapers claiming to give hints as to the motives and identity of the killer — remains unidentified.

Frederick Valentich

While on a routine training flight in 1978, Australian pilot Frederick Valentich suddenly disappeared, seemingly into thin air.

The strangest part? He was in radio contact with the Melbourne Flight Service up until his disappearance, and many believe what he described as happening to be a clear indication of an alien abduction.

As the Associated Press reported at the time, some officials assume Valentich was likely disoriented and flying upside down, thus describing his own reflection in the water to the flight service in Melbourne.

Either way, remains of his plane have never been found. So his disappearance is still a mystery.

K for Kryptos
Wikimedia commons

Just outside the headquarters of the Central Intelligence Agency in Langley, Va., is an “encrypted sculpture” known as Kryptos.

Kryptos, which is Greek for hidden, was dedicated outside the agency’s headquarters in 1990 and contains four coded messages. To this date, only three of the four messages have been decoded.

The still mysterious fourth message continues to capture the American imagination. In fact, popular novelist Dan Brown referenced the sculpture in his 2009 best-seller “The Lost Symbol,” and it has been alluded to in various other television shows, books and movies.

What's the frequency, Jerry?

As a volunteer for the Search for Extra Terrestrial Intelligence Institute, Jerry Ehman, a professor at Ohio State University, stumbled upon something that perplexes scientists to this day.

In August 1977, Ehman recorded and tracked a frequency “30 times louder than the ordinary noise of deep space,” ccording to NPR.a That might not sound too impressive to laymen, but to Ehman and other scientists who have studied the case, it was quite a find. Not only was the frequency’s intensity surprising, but the fact that the source has never been identified, and the fact that it has never been repeated, has left the occurrence shrouded in mystery.

A day at the beach
Wikimedia commons

In December 1948, an unidentified man was found on Somerton Beach in Adelaide, South Australia. But the case of the found body in Somerton Beach wasn’t just about identifying a dead man. A slew of strange clues were discovered with the body, leading investigators on a fruitless quest to understand where the man came from and why.

Among the strange clues was a small piece of paper found in the man’s trousers that read “Tamam Shud,” a phrase meaning “finished,” most notably used in a collection of Persian poems known as the “Rubaiyat of Omar Khayyam.”

During the media frenzy surrounding the investigation, a man came forward having found, in the back of his car, a copy of the book of poems that matched the paper found on the body. The man claimed to have no knowledge of how the book had found its way to his car and turned it in to the authorities. In the back of the book, an incoherent, or possibly unfinished, code was found. The body remains unidentified to this day.

Hanging with Mr. Cooper
Associated Press

n 1971, an unidentified man whom the media named “D.B. Cooper” hijacked a Boeing 727 airplane leaving Portland International Airport in Portland, Ore., collected a $200,000 ransom and disappeared. After receiving the ransom money, the hijacker released all the passengers and requested that the plane once again take flight. Once in the air, the hijacker escaped presumably out the aft door. Though a thorough investigation was conducted, he was never found.

To this day, the disappearance of D.B. Cooper is the only act of air piracy in American history to go unsolved.

America's lost sweetheart
Associated Press

Likely the most famous unsolved mystery on this list, the story of Amelia Earhart is nothing short of an American legend that has captured the imagination for generations.

On July 2, 1937, Amelia Earhart — who at the time was one of the most famous women in the country for her achievements in aviation — disappeared over the Pacific Ocean during an attempt to fly the circumference of the earth.

While many believe her disappearance to be easy explained by the dangerous nature of her flight — such as the possibility that the plane simply ran our of fuel — a lack of concrete evidence has left the reason for her disappearance up to the imagination.

The curious case of Ambrose Small
Wikimedia commons

In December of 1919, a little-known Canadian theater owner became one of the most famous missing persons in the first half of the twentieth century.

Ambrose Small was a self-made millionaire who, after selling off all of his theatrical holdings and having a brief visit with his lawyer, simply disappeared. With no ransom note or suicide letter, nor any money missing from his home or accounts, the case of the missing theater owner left little for local police to investigate.

In an attempt to understand the mysterious case, tabloids dug deep into his personal life, hoping to find answers as to why he might disappear. Nothing solid ever surfaced, and to this day no one really knows where, or why, he disappeared.