The United States has vowed to help solve the 75-year-old mystery of aviation legend Amelia Earhart after analysis of a photograph showed that she may have crashed on a remote Pacific island.

The next mystery would be whether Earhart and Noonan died quickly or... they lived as castaways

Earhart set off in 1937 from Papua New Guinea on a mission to circumnavigate the globe over the equator, its longest route. She and her navigator Fred Noonan were never seen again, despite a massive US search in the midst of the Great Depression.

US Secretary of State Hillary Clinton described the trailblazing female pilot as a personal and national heroine and offered moral support for an upcoming expedition to find the wreck of Earhart’s Lockheed Electra aircraft.

“Amelia Earhart may have been an unlikely heroine for a nation down on its luck but she embodied the spirit of an America coming of age and increasingly confident, ready to lead in a quite uncertain and dangerous world. She gave people hope and she inspired them to dream bigger and bolder,” Ms Clinton said.

“When she took off on that historic journey, she carried the aspirations of our entire country with her.”

Aviation enthusiasts from The International Group for Historic Aircraft Recovery said that they planned an underwater mission in July on the Kiribati archipelago’s remote island of Nikumaroro.

Ric Gillespie, the group’s executive director, said he came across a photograph of Nikumaroro taken in 1937 by a British expedition that − unlinked to Earhart − was assessing the uninhabited island for potential settlement.

Mr Gillespie said he saw what he thought was a simple “blob” on the picture. But after a closer analysis, Mr Gillespie said he believed it showed landing gear from the ill-fated Electra.

He called the evidence “compelling, but circumstantial” and promised to search the entire area around Nikumaroro.

“There are some very smart people who think we’re wrong about this, but there are some very smart people who think we’re right,” Mr Gillespie said.

“The only thing we can do is make a best effort to go and search and look and see what we can find.”

The next mystery would be whether Earhart and Noonan died quickly or − as generations of history buffs have imagined − they lived as castaways.

Ms Clinton and Mr Gillespie spoke with Kiribati’s Foreign Secretary Tessie Lambourne, who hoped that the search would not only find the wreckage but also put the remote nation on the tourist map.

“Nikumaroro atoll is a place of which few have heard. However, we are very hopeful that (search) efforts will change the situation,” she said.

But it is hardly the first lead to emerge on Earhart. Ms Gillespie’s group earlier announced what they had found what they thought were bones on Nikumaroro, but laboratory tests could not conclude that they came from humans.

Robert Ballard, the oceanographer who discovered the remnants of the Titanic in 1985, offered his support for the mission but said that he had long considered it virtually impossible to find Earhart’s plane.

Mr Ballard said that the area in which Earhart crashed was far vaster than the regions he had searched before.

The US government offered assistance in analysing the photographs and negotiating with Kiribati, but the search is funded by private donors, officials said.

Kurt Campbell, the assistant secretary of state for East Asian and Pacific affairs who took interest in the project after a trip to Kiribati, said that the State Department was optimistic but also clear-eyed about the search.

“It’s been one of the great mysteries for 75 years − probably the last great unsolved mystery of the 20th century,” he said.