1. Amelia Earhart's plane. 

On July 2, 1937, Amelia Earhart disappeared while attempting to circumnavigate the Earth. She almost completed the journey, too – just 7,000 miles to fly from Lae, New Guinea to Oakland, California. But something tragic happened over the Pacific. Earhart and Fred Noonan, her friend and navigator, never made it to Howard Island where a U.S Coast Guard ship was waiting for them.

The distance between the two islands was not far, but the plane seemingly disappeared into thin air. Of course, wild theories abound, but some scientists think that Nanoon overestimated when calculating how much gas was left in the tank. Other believe that they made a mistake and veered off-course of Howard Island and into uncharted waters.

President Roosevelt launched a two-week search for wreckage but to no avail. Explorers continue to seek the lost Lockheed 10E Electra.

Officially, the U.S government believes that Earhart crashed into the ocean. Historical investigators have other ideas, including the theory that they landed on an island occupied by the Japanese and were hauled away as prisoners or executed on the presumption that they were American spies.

The truth about Amelia Earhart's vanishing may never be uncovered.

2. D.B Cooper's disappearance. 

Mystery surrounds the most daring con ever played. In 1971, the now infamous D.B Cooper bought a plane ticket in Portland and headed to Seattle. After he and 36 other passengers boarded the aircraft, he quietly slipped a note to the unsuspecting flight attendant that he had a bomb in his suitcase. His demand, in return for the lives and safety of the people aboard, was $200,000, four parachutes, and a flight to Mexico.

When the jet landed in Seattle, each party kept their word. The FBI granted him his request and he freed the passengers. Only Cooper and the pilots remained as Flight 305 took off towards Mexico at low altitude. D.B strapped on his parachute and jumped out of the plane before it reached the border; some speculate that it was over Nevada at the time.

To make things even more interesting, Cooper purposefully jumped out during a major thunderstorm. He was never seen again. If he had died in the storm, surely a body would have been found by now? The story goes that he lived out his years under a new identity with plenty of cash. The only information the FBI has on Mr. Cooper is that he was a tall, white man in his 40's with brown eyes who ordered a bourbon and soda on the plane.

3. The vanishing crew of "Mary Celeste."

Captain Morehouse couldn't believe his eyes when he looked upon the choppy waters and saw the Mary Celeste. The ship had left port a week prior and should have docked in Italy by now. He sent his crew aboard the vessel and they reported it empty. The Mary Celeste was transporting over 1,000 barrels of industrial alcohol which remained in the vessel's cargo area. The crew had seemingly vanished.

A lifeboat was missing, but no supplies were stolen and the sailors' personal belongings were still in their bunks along with a half year supply of food. This rules out the possibility of piracy which was uncommon at the time in 1872. The boat was largely intact and not subject to any harsh storms that would warrant jumping ship.

The only remaining theory suggests mutiny. No evidence of foul play or aggression from crew members was ever recorded; family of the disappeared said no one had any reason to rebel as they were content with their jobs. Why the crew of the Mary Celeste vanished has yet to be solved.

4. The Voynich manuscript.

Created in the 15^th century, the Voynich manuscript remains one of the oldest enigmas today. The manuscript is a book from the 1400's written in an unknown language or code. Parchment was expensive and used only for important texts in that period, so whoever penned this conundrum must have been wealthy, educated, and skilled.

The troubling aspect for scholars is the fact that no one, since its discovery in 1912, has been able to decipher it. This includes numerous attempts by cryptographers and code breakers from WWII. Pictures of plants lead scientists to posit that it is a book of ancient medicine while others believe it reveals the process of alchemy.

Historians theorize that it might have belonged to Leonardo Da Vinci as he was famous for writing in riddles. The Yale library houses the original Voynich manuscript, but copies are available if you are willing to pay $8,000. If you want to try to decipher the codex, take a look at the digitized version here.