Commercial aviation accidents are exceedingly rare. According to the International Air Transport Association (IATA), more than 30 million global passenger airline flights take off and land without incident each year, while only five fatal accidents involving loss of life to passengers and crew occurred in 2022.
While safety investigators are often able to determine causes of passenger airplane crashes, their task becomes more difficult when catastrophe strikes far from shore. In some cases when passenger flights failed to arrive at their destinations, it’s as if airliners have seemingly vanished into thin air—with no radio messages, no wreckage, no survivors and not even oil slicks to offer clues to their ultimate fates.
The following eight passenger flights are among the most notable unsolved mysteries in commercial aviation history.
1. EgyptAir Flight 804 (May 19, 2016)
Although the digital flight data and cockpit voice recorders were recovered from the wreckage of the Airbus 320 carrying 66 people from Paris, France, to Cairo, Egypt, mystery still surrounds what caused the aircraft to plunge into the 13,000-foot-deep waters of the eastern Mediterranean Sea.
In the investigation’s early months, Egypt’s aviation ministry pointed to a terrorist bomb as the most likely cause and announced that traces of explosives had been detected on victims’ remains. However, France’s civil aviation accident bureau reported in 2018 that a rapidly spreading fire on the flight deck most likely caused the crash.
Moments before the plane vanished from radar, air traffic controllers received messages relayed from the plane’s onboard reporting system that smoke had been detected. Recorders substantiated the presence of smoke on board the plane, and French authorities said the aircraft took an unusual sharp left turn, followed by a 360-degree turn to the right before it was lost from radar. That would have been an odd trajectory if a bomb had exploded, but investigators said the path indicates a rapid descent to vent smoke. A subsequent French investigation attributed the cause of the crash to a pilot smoking a cigarette in the cockpit, compounded by a leaking oxygen mask.
2. Malaysia Airlines Flight MH370 (March 8, 2014)
The disappearance without a trace of the Boeing 777 carrying 239 people en route from Kuala Lumpur, Malaysia, to Beijing, China, captured worldwide attention and continues to confound investigators. After the aircraft’s final communication over the South China Sea 38 minutes after takeoff, military radar showed it subsequently veered dramatically off course and flew westward toward the Indian Ocean before the signal was lost.
Some aviation experts believe it may have flown for several hours before running out of fuel over the southern Indian Ocean. The largest and most expensive search in aviation history, which included 334 search flights and the deep-sea scouring of 46,000 square miles of ocean floor, uncovered no wreckage and no answers to what happened to the airplane.
About 20 pieces of debris believed to have come from Flight MH370 have been recovered on the islands of Madagascar, Mauritius, Réunion and Rodrigues and along the African coastline as far away as Tanzania. A 2018 Malaysian government report offered no conclusion about the flight’s fate, although it ruled out mechanical or computer failure and concluded that the aircraft’s manual deviation from its intended flight path and the switching off of a transponder “irresistibly point” to “unlawful interference,” which could indicate a hijacking or a rogue pilot.
3. Flying Tiger Line Flight 739 (March 16, 1962)
Traveling on a charter flight operated by the Flying Tiger Line rather than a military aircraft, 93 U.S. Army Rangers dispatched on a secret mission in the early days of the Vietnam War departed California’s Travis Air Force Base bound for Saigon. After a refueling stop in Guam, their Lockheed L-1049 Super Constellation that also carried 3 members of the South Vietnamese military and 11 crew members never arrived at its next stopover—Clark Air Base in the Philippines—although flying conditions were ideal and no distress signal was ever received.
The disappearance sparked the largest peacetime air-and-sea rescue mission in the Pacific Ocean since Amelia Earhart vanished in 1937. The 1,300-person search party scoured 144,000 square miles and turned up nothing. An Italian crew aboard an oil super tanker reported seeing an “intensely luminous” explosion in the sky and two flaming objects plunging to the ocean around the location of the plane when it disappeared. Since another Flying Tiger plane had crashed in Alaska only hours earlier, killing one of the seven people aboard, sabotage was considered, but the Civil Aeronautics Board ultimately could not determine a probable cause because of the lack of any recoverable evidence.
4. Pan Am Flight 7 (November 9, 1957)
The Boeing 377 Stratocruiser that took off from San Francisco to Honolulu with 36 passengers and 8 crew members on the first leg of an around-the-world flight was the lap of luxury. Passengers aboard the “ocean liner of the air” enjoyed 60 inches of legroom, reclining sleeper seats, a horseshoe-shaped cocktail lounge and 7-course dinners that included caviar and champagne. The Clipper Romance of the Skies was about halfway through the flight when radar contact was suddenly lost without a distress call from the plane.
After a five-day search, a U.S. Navy carrier spotted floating debris and recovered 19 bodies nearly 1,000 miles east of Honolulu. Most of the victims were wearing life vests, indicating that the plane had been prepared to hit the Pacific Ocean. The aircraft and the remaining 25 people aboard were never found. Although testing revealed elevated levels of carbon monoxide in several of the recovered bodies, the Civil Aeronautics Board found “no evidence of foul play or sabotage.”
5. Canadian Pacific Air Lines (July 21, 1951)
As the Korean War raged, a Douglas DC-4 took off from Vancouver, Canada, on a flight to Tokyo, Japan, to assist in the Korean Airlift. Carrying 31 passengers and a 6-person crew, the Canadian Pacific airliner encountered rain, low visibility and icing conditions as it approached Anchorage, Alaska, for a refueling stop. The plane reported no issues as it checked in near the Alaskan panhandle about 90 minutes from arrival. It would never be heard from again. American and Canadian rescue teams searched for months but found no traces of wreckage.
6. Northwest Orient Airlines Flight 2501 (June 23, 1950)
As the pilot of the DC-4 prop plane carrying 55 passengers and a 3-person crew approached Lake Michigan around midnight, a powerful line of squalls loomed ahead. The storm’s severe turbulence and frequent lightning had already caused pilots of three other westbound flights to turn around. Near Benton Harbor, Michigan, the pilot of the Northwest airliner requested permission to lower altitude from 3,500 feet to 2,500 feet without stating a reason, but air traffic controllers denied the request because of other planes in the area. The pilot’s acknowledgment of the denial would be the last transmission received from the plane that was en route from New York to Seattle with stopovers scheduled for Minneapolis and Spokane, Washington. Minutes later, witnesses on the ground heard a sputtering aircraft “like a stock car with a blown head gasket” and saw a “terrific flash.”
The U.S. Coast Guard discovered oil slicks in Lake Michigan near Milwaukee and focused the initial search there. However, two days later search parties discovered blankets with the Northwest logo, foam rubber cushions and human remains 10 miles offshore of South Haven, Michigan, and the responders realized they had been looking in the wrong area of the lake for the plane. With visibility less than 8 inches in the murky lake bottom, divers could not locate the plane, and the U.S. Civil Aeronautics Board could only conclude that the cause of what at the time was the deadliest commercial airliner accident in American history was “unknown.” Over the past decade, sonar exploration of 300 square miles of the lake bottom near the suspected crash scene has identified 14 shipwrecks, but no sign of Flight 2501.
7. British South American Airways Star Ariel (January 17, 1949)
Long a “twilight zone” for mariners, the Bermuda Triangle continued to be the scene of mystery during the aviation age when airplanes vanished over the waters of the Atlantic Ocean between Bermuda, Puerto Rico, and the southern tip of Florida.
Although the pilot reported fine weather conditions, radio contact with the Star Ariel en route from Bermuda to Jamaica suddenly ceased an hour after the flight departed. British investigators could not find the wreckage of the Avro Tudor Mark IV or any sign of the 20 people on board. Without evidence, investigators were forced to conclude that the cause of the accident was unknown.
8. British South American Airways Star Tiger (January 30, 1948)
The Star Ariel crash came less than a year after the disappearance of another British South American airliner. The Star Tiger, with 31 people aboard, maintained normal radio communication shortly before entering Bermuda airspace on a flight from the Azores. The plane, however, never landed, and no distress message ever emanated from the Avro Tudor aircraft. A five-day rescue effort located no wreckage, and investigators concluded the fate of the airliner was “an unsolved mystery.” According to the official investigation report, “It may truly be said that no more baffling problem has ever been presented for investigation.”
