Airplanes are one of the biggest inventions of the twentieth century. Airplanes are the fastest modes of transportation, reducing significantly the number of hours spent on a journey. Unfortunately, in some cases, these planes have crashed or simply disappeared, giving rise to a multitude of conspiracy theories. Even after years of meticulous investigation, we still do not have answers. Today, we bring to you the 10 biggest aviation mysteries of all time.

1 Malaysian Flight MH370 took off from Kuala Lumpur bound for Beijing with 227 passengers on 8 March 2014. Almost an hour later, the Malaysian Airport Authority lost contact with the plane. Strangely, before its disappearance, the plane changed its direction several times. There are multiple theories, but no one knows the truth yet.

Malaysian Flight MH370 took off from Kuala Lumpur at 12:41 a.m. on 8 March 2014. The flight had 227 passengers on board. At 1:19 a.m., the last voice communication from the crew occurred. A few minutes later, the plane’s transponder was switched off, and from then on, there was no communication with the plane. Soon, Malaysian military radar lost contact with the plane.

Multiple countries joined in the attempt to find the flight. Strangely, just before the transponder was switched off, someone manually changed the direction of the plane. This created suspicion. Some claimed that the pilot committed suicide.

Few felt that the plane was shot down due to fear of terrorist attack, probably by North Korea. Nothing has been proved yet. In 2017, the authorities officially closed the search for Flight 370, leaving millions of people with answered questions. (1, 2)

2 A man with the pseudonym “D.B. Cooper: hijacked a Boeing 727 aircraft in the United States on 24 November 1971. He threatened to detonate a bomb and received a hefty ransom. Once he got the money, the hijacker released all passengers and ordered the crew to fly to Mexico. En route, he parachuted from the aircraft. His identity remains unknown.

A man with the pseudonym “Dan Cooper” boarded a Northwest Orient Airlines Flight 305 on 24 November 1971. The flight took off from Portland bound for Seattle, Washington. A few minutes after the takeoff, “D.B. Cooper” handed a note to a flight attendant in which he claimed to have a bomb in his briefcase. He opened the briefcase and it had some red wires and a battery. He demanded four parachutes and $200,000 in $20 bills.

The flight finally landed in Seattle. The airport authorities gave him the money and parachutes. He released all of the 36 passengers. He then asked four crew members to stay on board and fly with him towards Mexico City. He ordered the pilot to fly only under 10,000 feet. Around 8:00 p.m., somewhere between Seattle and the state of Nevada, he lowered the rear stairs and jumped. He then disappeared.

The FBI launched a manhunt to find the hijacker. First, the FBI speculated that he was a paratrooper. However, experts rejected the claim as an experienced skydiver would not have jumped at night as it was too dangerous. The FBI followed thousands of leads to find the man. After a 45-year FBI investigation, his identity, whereabouts, and motive other than the $200,000 remain unknown. Finally, the FBI closed the investigation in 2017. (1, 2)

3 EgyptAir Flight 99 crashed into the Atlantic Ocean on 31 October 1991, killing all 217 passengers and crew on board. Both the US and Egyptian aviation authorities had a clash over the cause of the crash. While Egyptian authorities blamed mechanical failure, the United States authorities suggested that the pilot committed suicide.

EgyptAir Flight 990 mysteriously plummeted into the Atlantic Ocean on 31 October 1991. It was a giant, twin-engine, Boeing 767 with 217 people aboard. It took off from Kennedy Airport, New York bound for Cairo. All 217 people on board died. Among the passengers were a large group of Egyptian military officers. Therefore, a suspicion arose that the plane was targeted by Egypt’s enemies.

According to American air authorities, it was a case of suicide by co-pilot Gamil al-Batouti. On recovering the cockpit voice recorder, American authorities found out that before the plane began its first descent. Gamil was heard stating repeatedly in the Arabic language, “I rely on God.” therefore signaling the co-pilot committed suicide.

However, Egyptian authorities rejected this theory completely. They discovered that the failure of the control mechanism led to the fatal incident. This clash in theories between American and Egyptian authorities led to confusion regarding the cause of the crash. (1, 2)

4 During a training exercise, a B47 Stratojet collided with another aircraft. The B47 Stratojet plane was loaded with a 1.69-megaton nuclear weapon. To land the flight, the plane needed to lighten the load immediately. So, the pilot ejected the nuclear weapon. The search team never found the weapon again.

After almost seven hours of a training exercise, a B-47 Stratojet plane was flying over Hampton County, US on 2 February 1958. Major Howard Richardson piloted the plane. Suddenly, the plane collided with a USAF F-86 Sabre jet.

Howard, on the B-47 plane, tried to land his plane safely. Howard soon realized that he needed to lighten his load to increase his chances of landing safely. That load was an almost 4-ton hydrogen bomb. The B-47 plane successfully landed in one attempt only, after Howard jettisoned the bomb.

This led to a massive search for the hydrogen bomb in the Atlantic Ocean. While some claimed that the bomb was fully functional, others said that it was disabled. On April 16, the military announced the search had been unsuccessful. In 2004, retired Air Force Lt. Colonel Derek Duke claimed to have found the possible resting spot of the bomb. However, until now, the bomb has not been recovered. (1, 2)

5 Five TBM Avenger torpedo bombers took off from Florida on 5 December 1945. During their journey, the captain realized that his compass was not working. After some time, the air controllers lost contact with the planes. More than a hundred planes looked for the five planes, but they were never found.

Five TBM Avenger torpedo bombers, collectively called “Flight 19” took off from an air station in Florida on 5 December 1945. They were to conduct a bombing trial. Lieutenant Charles C. Taylor led the mission. The planes were flying smoothly, without any disturbance. Just before their return, Flight 19 dropped their practice bombs.

However, when they turned north to cover the second phase of the journey, they found themselves in a strange situation. Charles felt that his compass had stopped working. He informed the authorities that Flight 19 planes were probably flying in the wrong direction. Their difficulties increased when it started raining with heavy winds and clouds.

Charles ordered the planes to move towards the east. So, all the other planes followed him. However, by evening, none of the planes could be contacted. Search planes tried to hunt for the missing patrol but nothing happened.

These disappearances led to the emergence of a plethora of theories around the Bermuda Triangle. In 2007, Peter Leffe, an aviation expert, claimed to have solved the case. He felt that Charles was confused about his location and made wrong decisions.

It is due to his fault that all the planes disappeared. However, no official statement has been released regarding their disappearance, making this one of the biggest unsolved aviation mysteries. (1, 2)