AP file

This undated file photo shows Amelia Earhart. A new expedition is attempting to find the wreckage of the plane she flew in her attempt to circumnavigate the globe in 1937.

Seventy-five years after Amelia Earhart went missing over the Pacific Ocean while attempting to circumnavigate the globe, a new expedition will search the waters in hopes of resolving the longstanding mystery of what happened to the American aviation pioneer.

The Niku VII expedition will search the underwater reef slope off the west end of Nikumaroro, formerly Gardner Island, an uninhabited coral atoll in the Pacific, looking for signs of wreckage from Earhart’s Lockheed Electra.

The expedition is being led by Richard Gillespie, executive director of The International Group for Historic Aircraft Recovery, or TIGHAR (pronounced “tiger”),  a Wilmington, Del.-based nonprofit group that promotes aviation archaeology and historic preservation.

“The primary search area is based upon the hypothesis that the aircraft landed safely on the reef and remained there for several days before being washed over the reef edge by rising tides and surf,” TIGHAR says on its website in explaining the mission. “Aircraft debris reportedly found and used by island residents in later years, and aircraft parts found by TIGHAR in the abandoned village strongly suggest that the aircraft broke up in the relatively shallow surf zone.”

Earhart became the first woman to fly solo across the Atlantic Ocean in May 1932, when she took off from Harbour Grace, Newfoundland, and landed the next day in Londonderry, Northern Ireland.

In March 1937, she attempted to fly around the world in a twin-engine Lockheed Electra, but a tire blew out during takeoff from Hawaii and she crashed.

After her plane was repaired, Earhart, then 39, set out on a second attempt from Miami in June 1937 with navigator Fred Noonan. They were on the last leg of the flight when the plane went down on July 2, 1937, while approaching Howland Island, a remote coral island in the central Pacific Ocean about 1,700 nautical miles southwest of Honolulu.

U.S. Coast Guard and Navy ships searched the area but turned up no sign of the crew or the plane. Earhart’s disappearance remains a mystery to this day.

Many researchers believe Earhart’s plane ran out of fuel and the pair ditched at sea. But other theories abound, with some conspiracy theorists suggesting Earhart was caught and held by the Japanese as a spy.

The expedition led by TIGHAR assumes that the pair reached Gardner Island, then a British possession, and survived for an unknown period of time.

Crews using underwater robots will search the waters with high-frequency sonar and take black-and-white photos down to a depth of nearly 5,000 feet (1,500 meters), according to TIGHAR. The expedition will be able to examine sonar targets using high-definition video down to a depth of 3,300 feet (1,000 meters).

The object of the expedition is to locate, identify and photograph any wreckage found. There are no plans to recover any wreckage.

"What we're hoping for is to come back with good imagery, photographs, of wreckage that's conclusively, unquestionably pieces, at least, of Amelia Earhart's Lockheed Electra aircraft; that's the goal," Gillespie told the BBC.

A documentary on the expedition will be broadcast on the Discovery cable television channel.

More content from msnbc.com and NBC News:

• Thousands of veterans failing in new battlefield: college
• Is gay marriage debate driving young people from church?
• Military plane crashes while battling South Dakota wildfire
• Video: Wildfire evacuees return to charred homes
• Chicago gun buyback raises money for NRA kids camp
• Report: Homeless man scammed luxury hotel stays at others' expense

Follow US News on msnbc.com on Twitter and Facebook

WASHINGTON -- Following new analysis of a photo that could show wreckage of Amelia Earhart's plane, the Obama administration on Tuesday said it was backing a search this summer to hopefully solve the mystery of America's greatest female aviator.

"We can be as optimistic and even audacious as Amelia Earhart," Secretary of State Hillary Rodham Clinton said at a ceremony in Washington, D.C., to announce U.S. support for the expedition. "There is great honor and possibility in the search itself."

The search by The International Group for Historic Aircraft Recovery will focus on the remote island of Nikumaroro, in what is now the Pacific nation of Kiribati.

The group believes Earhart and her navigator Fred Noonan might have managed to land on the island, then known as Gardner Island, and that they could have survived for a short time after disappearing on July 2, 1937.

Other historians believe they crashed into the ocean. But conspiracy theories, including claims that they were U.S. government agents captured by the Japanese before World War II, abound despite having been largely debunked.

The International Group for Historic Aircraft Recovery

This 1937 photo was presented Tuesday as having been analyzed by experts to reveal an object in the water, not easily visible at this scale, showing what might be the landing gear and a wheel from an aircraft.

New analysis of a photo taken at Nikumaroro three months after the disappearance shows what some people believe could be a strut and wheel of the plane protruding from the water, the group says. State Department analysts helped examine the photo.

The hypothesis is that the plane crashed on a reef before eventually being washed deeper into the sea.

The group hopes that probes down the reef slope will reveal larger aircraft parts such as the engines lying in a dim "twilight zone" about 300 yards below the ocean surface.

Renowned oceanographer Robert Ballard, who discovered the wreckage of the Titanic and the Bismarck and is advising the Earhart expedition, said the new analysis of the photograph could be the equivalent of a "smoking gun" as it narrows the search area from tens of thousands of square miles to a manageable size.

In 2010, bone fragments were found on the island that the group believes might be of Earhart or Noonan. Other artifacts have been recovered there as well that suggest the two might have lived for days or weeks after landing on a reef.

The privately funded group is putting up $500,000 for the search. The U.S. won't provide money but will offer limited logistical support. Transportation Secretary Ray LaHood joined Clinton at the ceremony.

Ric Gillespie, the executive director of the group, said the new search is scheduled to last for 10 days in July and will use state-of-the-art underwater robotic submarines and mapping equipment. The Discovery Channel will film the expedition for a television documentary, he said. He acknowledged that the evidence was circumstantial but "strong" but stopped well short of predicting success.

"The most important thing is not whether we find the ultimate answer or what we find, it is the way we look," he said. "We see this opportunity to explore ... the last great American mystery of the 20th century as a vehicle for demonstrating how to go about figuring out what is true."

"Back in 1937, in the painful recovery from the Great Depression, Amelia Earhart's courage and determination inspired the American people," he added. "Well, hard times are here again and we need that type of courage and determination again ... we're going to try our best to find her, not for ourselves, but for you," the public.

Details about the planned expedition
Explainer: Earhart and other famous mysteries

The expedition will coincide with the 75th anniversary of Earhart's departure on the ill-fated attempt to become the first woman to fly around the world.

NBC's Catherine Chomiak and The Associated Press contributed to this report.

More content from msnbc.com and NBC News:

• Feds to probe death of unarmed Florida teen
• Could this new tower be the future of cities?
• 'Kratom' leaf making presence felt in US emergency rooms
• Wife of Afghan massacre suspect: 'Out of character'

Follow US News on msnbc.com on Twitter and Facebook

Anonymous / AP file

Amelia Earhart in an undated photo.

The State Department plans to join a new effort to find the plane of pioneering aviator Amelia Earhart, 75 years after she mysteriously disappeared over the South Pacific.

Secretary of State Hillary Rodham Clinton and Transportation Secretary Ray LaHood will take part in a ceremony Tuesday morning announcing the joint public-private search at the State Department, The Wall Street Journal reports. The event, "Amelia Earhart, a Pacific Legacy," which is pitched as a celebration of the U.S.'s pan-Pacific ties, will be streamed live at 9 a.m. on the State Department's website, a spokesman for the agency said.

Earhart's twin-engine Lockheed vanished July 2, 1937, as she and her navigator, Fred Noonan, left New Guinea (now Papua New Guinea) on their way to Howland Island in the South Pacific as part of an attempt to circle the Earth.

Bing Maps

The search will center on the Nikumaroro Islands in the South Pacific.

The half-million-dollar search, financed with private funds, will begin in July. The key area is the Pacific atoll of Nikumaroro between Hawaii and Australia, The Journal reports:

A search team will concentrate on the deep waters near Nikumaroro, which was the site of a 2010 search that focused on coral reefs and nearby shallow waters, these people said.

The search will be spearheaded again by the International Group for Historic Aircraft Recovery, which has championed the theory that the renowned female aviator and Fred Noonan, the other crew member on the July 1937 flight, ended up on or near the west coast of the island, formerly called Gardner Island.

More content from msnbc.com and NBC News:

• 'Kratom' leaf making presence felt in US emergency rooms
• Mom: Trayvon was killed because of 'the color of his skin'
• Fuhgeddaboutit! NJ top state for fighting corruption
• Woman found dead with three kids was 'good mom'

Follow US News on msnbc.com on Twitter and Facebook