The fate of pioneering pilot Amelia Earhart has remained a mystery for decades. After achieving worldwide fame by becoming the first female pilot to fly solo across the Atlantic, Earhart vanished along with her navigator, Fred Noonan, over the Pacific Ocean on 2 July 1937. The pair were four months into a daring attempt to circumnavigate the globe.

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Generations of aviation experts and conspiracy theorists have speculated about what happened to the flight, with some claiming the pair were really spies who crash-landed on a Japanese island where they were captured and executed. US government officials concluded they crashed into the sea and were killed.

However, after 22 years of research, The International Group for Historic Aircraft Recovery (TIGHAR) believes it has uncovered their true fate.

The pair planned to land halfway between Hawaii and Australia on Howland Island as part of their mission.

However, according to TIGHAR, they failed to find the island, and running out of fuel instead continued along the same navigational line, landing on uninhabited Gardner Island, also known as Nikumaroro, 350 miles away.

They sent hundreds of distress signals from the Electra plane for three days, according to the group, with radio bearings taken on the signals indicating they had crossed the island. The signals were picked up as far as Melbourne and Texas, according to TIGHAR's Ric Gillespie.

READ MORE: Could British explorers have saved Amelia Earhart as she lay dying on a Pacific island?

Among those who picked up the distress calls was a 16-year-old girl in Florida, listening to her radio at home. The teenager transcribed Earhart's indistinct message, which included the word New York repeated several times.

A week after the pair's disappearance, US Navy planes searching for them flew over the island, but by that time the signals had stopped. The crews saw evidence of human habitation on the island but no plane. They were not aware that the island had not been inhabited since 1892.

Amelia Earhart
Amelia Earhart is believed to have died as a castaway after crashing her plane on an island in the Pacific Getty images

TIGHAR believes Earhart and possibly Noonan survived the crash, and lived as castaways on the remote island, eating clams, turtles, fish and birds, and drinking rainwater.

It believes that Earhart died in a makeshift camp on the south-east of the island, and the plane was swept off the edge of the reef that rings the island. The group plans to search the seabed off the island with a submarine for remains of the plane.

In 1940, a British Colonial Service officer said he found a partial skeleton on the island, along with a campfire, animal bones, a box containing a sextant consistent with the type used by Noonan, and remnants of male and female shoes.

Earhart and Noonan were declared legally dead on 5 January 1939, with the US government concluding that they had run out of fuel and crashed into the sea.