Amelia Earheart disappeared during a trans-pacific flight 75 years ago. Now, investigators think they've found the key clue that will lead them to solve one of America's greatest mysteries.

In a news conference in Washington Tuesday, Ric Gillespie, executive director of The International Group for Historic Aircraft Recovery (TIGHAR), said a new enhanced analysis of a photo taken on the Pacific atoll of Nikumaroro, formerly Gardner Island, three months after Earhart and navigator Fred Noonan disappeared, may show the landing gear of her Lockheed Electra exposed from a reef.

We found some really fascinating and compelling evidence, Gillespie said in reference to the photo.

Finding the airplane would be the thing that would make it conclusive, he added.

According to Gillspie, the photo, which was taken by a British survey team in October 1937, was seen by Earhart researchers many times before, but had not registered as anything significant.

It wasn't until investigators took a second look at the photo in 2010, that their suspicions were triggered.

After being checked by U.S. State Department experts, the determination was that the component in the picture was that of the landing gear of a Lockheed Electra.

According to report done by the Discovery News, nine archaeological expeditions to Nikumaroro by Gillespie and his team resulted in the recovery of a number of artifacts which, combined with archival research, provide strong circumstantial evidence for a castaway presence.

We found archival records describing the discovering in Nikumaroro in 1940 of the partial skeleton and campsite of what appears to have been a female castaway, Gillespie said in the Discovery News interview.

We identified the place on a remote corner of the atoll that fits the description of where the bones and campsite were found. Archaeological digs there have produced artifacts that speak of an American woman of the 1930s, he said.

Determined to solve the Earhart mystery once and for all, Gillespie and his team are heading out on a new expedition, this time concentrating on the aviator's plane.

Secretary of State Hillary Clinton said she was thrilled to welcome the group of scientists launching a new exhibition into the disappearance of aviator Amelia Earhart 75 years ago.

Wow, Clinton said in Washington, D.C., today. This is an exciting day. We haven't had an event quite like this one before and that's what I love about it.

Partaking in the privately funded half-million dollar expedition will be the U.S. Navy's primary deep ocean search and recovery contractor, Phoenix International.

TIGHAR and Phoenix will depart on July 2, from Honolulu on a University of Hawaii research vessel.

The date marks 75 years to the day after Earhart was last heard from.