A scrap piece of metal could be the clue that solves one of aviation's longest mysteries - the disappearance of Amelia Earhart.

A fragment of Amelia Earhart’s lost aircraft — one of the greatest mysteries of all time — has been identified for the first time ever since the aviation pioneer’s plane vanished over the Pacific Ocean in 1937.

Earhart’s twin-engined Lockheed Electra disappeared without trace while she was attempting to circumnavigate the globe.

Theories have abounded over the years about what happened to Earhart who was the first female to fly solo across the Atlantic Ocean, and her navigator Fred Noonan on the doomed flight.

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New research suggests that a patch of metal recovered in 1991 from Nikumaroro, a coral reef uninhabited atoll in the south-western Pacific republic of Kiribati, belongs to Earhart’s plane, Discovery News reports.

The International Group for Historic Aircraft Recovery has been studying the scrap of aluminium, found on the tiny atoll which lies between Hawaii and Australia, for the past 25 years.

Researchers now believe the metal sheet, which bears distinctive rivets, could be the same patch of metal that appears in the Miami Herald photograph of Earhart’s Electra.

To test their theory, TIGHAR researchers travelled to Wichita Air Services in Earhart’s home state of Kansas to compare the dimensions of the sheet of metal to the components of a Lockheed Electra being restored to airworthy condition. They found that the rivets appeared to match those of the patch that would have been used to fix Earhart’s plane.

“This is the first time an artefact found on Nikumaroro has been shown to have a direct link to Amelia Earhart,” Ric Gillespie, executive director of TIGHAR, told Discovery News.

“The Miami Patch was an expedient field repair. Its complex fingerprint of dimensions, proportions, materials and rivet patterns was as unique to Earhart’s Electra as a fingerprint is to an individual,” he said.

The breakthrough would disprove the long-held theory that Earhart and Noonan crashed in the Pacific Ocean after running out of fuel somewhere near their target destination of Howland Island.

Instead, they would have made a forced landing on Nikumaroro’s coral reef. The two would have become castaways and eventually died on the atoll, which is around 550 kilometres southeast of Howland Island.