On Friday, an international team of search-and-rescue submarines scoured the floor of the Atlantic Ocean for wreckage from Air France’s missing Flight 447. Debris originally thought to belong to the airplane has turned out to be unrelated flotsam. Authorities speculated that the vanished aircraft and its black box may never be found, leaving the flight’s victims and their families in limbo forever. But at least they’re not alone. Here are seven of the world’s most perplexing unsolved mysteries that took place high in the sky.

AMELIA EARHART Aviation’s first great mystery.

As the aeronautical yin to Charles Lindbergh’s yang, a bestselling author, and cherished national hero, Amelia Earhart was on top of the world in 1937—and then she tried to fly around it and never returned. Earhart’s first attempt at the epic flight failed due to mechanical errors that some say were the famed pilot’s fault. On her second attempt, Earhart logged 22,000 continent-skipping miles with navigator Fred Noonan before a pitstop planned for the South Pacific’s Howland Island. During her approach, Earhart radioed, “We must be on you, but cannot see you. Gas is running low.” In her last known transmission, Earhart’s voice was confident—and then the line went dead. An international search helmed by the United States Navy turned up little, and urban legends on Amelia Earhart’s fate—Did she and Fred run off together? Did she crash and sink?—fuel the ongoing pop culture fascination that culminates this October in Hilary Swank’s portrayal of the female pilot in Amelia.

GREECE’S GHOST PLANE After everyone on board dies, Helios 522 drifts to catastrophe.

It’s the stuff nightmares and Fox TV series are made of: a jumbo-jet cruising over a densely populated region of the world, every person on board dead in their seats. When pilots on Helios Airways’ Flight ZU 522 failed to flip the compression switch on their aircraft’s oxygen supply, a sudden drop in cabin pressure rendered everyone on board unconscious. Flight ZU 522, en route from Cyprus to Prague, cruised on autopilot for two hours before running out of fuel and crashing outside Athens. When ground control first noticed the wandering airliner’s peculiar flight pattern, the Greek air force deployed a pair of fighter jets to trail it and gather information. The fighter pilots reported what the Times of London called the “eerie spectacle” of autopilot gone rogue: “The pilot’s seat was empty and the first officer was slumped over the controls.”

THE UFO Australian pilot reports something “just orbiting on top of me” before vanishing.

In October 1978, aviation enthusiast Frederick Valentich embarked on what should have been a puddle jump from Melbourne’s Moorabbin Airport to Tasmania’s King Island. Instead, he went down in paranormal history when he and his aircraft vanished after a harrowing UFO sighting. According to Moorabbin officials, flying conditions on that day were pristine. At 7 p.m., Valentich radioed Moorabin flight control to inquire about a “large aircraft” approaching from the east with “four bright landing lights.” Flight control reported no known aircrafts in the vicinity, but Valentich was adamant: “It seems to me that he’s playing some sort of game, he’s flying over me—two, three times.” As his radio transmission cut in and out, Valentich described a “thing… just orbiting on top of me… it’s got a green light and sort of metallic, all shiny on the outside.” Twenty minutes later, the transmission degraded into 17 straight seconds of raspy open microphone followed by an “unexplained sound” that “abruptly terminated the voice communication.” Following the news of Valentich’s disappearance, dozens came forward claiming to have witnessed colorful lights in the sky that day, allegedly chasing a small airplane. Australia’s search-and-rescue missions revealed no trace of Valentich’s Cessna, and to this day ufologists bounce theories about military warcrafts, airborne drug traffickers, and alien spaceships. At the time of his disappearance, even Valentich’s father thought aliens stole his son.

STAR DUST, STAR TIGER, AND STAR ARIEL The Bermuda Triangle legend begins.

During World War II, aviation technology grew faster than navigational instruments could keep up. The result was a series of frightening mishaps, including a legendary trio of British South American Airlines passenger jets that vanished over the course of three years in and around the Bermuda Triangle. In 1947, Star Dust—a civilian version of WWII’s Lancaster bomber, staffed with Royal Air Force veterans—radioed four minutes ahead of its charted arrival in Santiago, Chile, to say it was on time. But Star Dust never arrived. One year later, 1948 BSAA’s Star Tiger charted a course from Santa Maria to Bermuda amid torrential rain; blown off course by wind and lagging behind schedule, Star Tiger’s crew charted a new course manually via celestial navigation, eventually losing radio contact and disappeared with nary a distress message. After Star Tiger’s disappearance, the British government temporarily grounded all Lancaster-modeled airplanes—but let them back in the sky in time for a third BSAA tragedy: In 1949, BSAA’s Star Ariel disappeared while flying from Bermuda to Jamaica on a clear January day. The BSAA’s three vanished airplanes sealed the legend of the Bermuda Triangle in the popular imagination. Since then, however, some discoveries have knocked the rumored curse down a peg: In 1998, an Argentinean mountaineer uncovered wreckage from Star Dust’s engine in the Andes Mountains. Since then, remains from nine of Star Dust’s 11 missing passengers are thought to have been recovered.

ALIVE IN THE ANDES After crash, Uruguayan rugby team turns to cannibalism.

The mystery of Uruguayan Air Force Flight 571 lies not in the logistics of the chartered jet’s crash in the Andes, but in the traumatized psyches of its survivors. Flight 571 was carrying a team of 45 Uruguayan rugby players and crew members when it crashed into the icy slopes of the Chilean-Argentine border in 1972. An avalanche and inclement weather forced rescue squads to give up rescue efforts after eight days—little did they know that the 29 passengers who survived the initial impact were in the midst of a tooth-and-nail fight for survival. In Alive: The Story of the Andes Survivors, Piers Paul Read explains how the remaining survivors battled hopelessness, hunger, frostbite, mortal wounds, and fatigue—resorting at several points to cannibalism—until, 72 days later, two survivors emerged from Chile’s frozen mountains and summoned rescuers to the remaining 14 in their party. After Read’s first literary treatment of the episode, a movie, documentary, and second book have all chronicled Flight 571’s survivors.

Maureen O'Connor is an assistant editor at The Daily Beast.