Amelia Earhart
The fate of Amelia Earhart remains one of America's most baffling unsolved mysteries. Wiki Commons

A research group hoping to find the remains of Amelia Earhart's plane from her final fatal flight is now returning to Hawaii without the results they were hoping for, according to the Associated Press.

The $2.2 million expedition lead by the International Group for Historic Aircraft Recovery continues to believe that Earhart crashed onto a reef off a remote island in the Pacific Ocean, with this month marking 75 years since her disappearance.

This is just sort of the way things are in the world, president of the group Pat Thrasher said to the AP. It's not like an Indiana Jones flick where you go through a door and there it is. It's not like that-it's never like that.

Although the TIGHAR is believed to have not found any remains of Earhart's aircraft, the team compiled a significant amount of sonar data and video. Searchers plan to examine these finds on their way back to Hawaii to ensure that they pick up on clues that can be easily missed upon first glance.

The recent expedition will not be the group's only attempt to put to rest the shroud of mystery that surrounds Earhart's disappearance. According to the AP, another voyage is being planned for next year to search the area where it is believed Earhart survived for a short while after the crash.

Thrasher posted updates about the journey to the group's website that reveal it was cut short due to dangerous underwater terrain and repeated technical difficulties with equipment. This caused delays and the group was only able to conduct their voyage for five days rather than the planned 10-day excursion.

One incident almost left a team member stranded when a vehicle wedged itself into a small cave and needed to be rescued. This was only one day after the same vehicle squashed its nose cone against the ocean floor, the AP reports.

The rescue mission was successful-but it was a real cliffhanger, founder of the group Ric Gillespie wrote in an email last week. Operating literally at the end of our tether, we searched for over an hour in nightmare terrain: a vertical cliff face pockmarked with caves and covered with fern-like marine growth.

The privately funded trip was supported by the U.S. State Department, the AP reports. The mission launched earlier from Honolulu and used 30,000 pounds in specialized equipment and a University of Hawaii ship typically used for ocean research.

The group's thesis says that Earhart and her navigator Fred Noonan landed on a reef near the Kirbati atoll of Nikumaroro and survived for a short time.

The group had previously found evidence of a woman castaway from the 1930s, but it has not been proven that this is Earhart.

We've found artifacts of an American woman castaway from the 1930s but we haven't found anything with her name on it, Gillespie said to Reuters earlier in July. We've tried to get contact DNA from things that were touched, and it didn't work. The environment was too destructive. The recovered bone samples were too small. The logical thing is the airplane.

But that doesn't mean researchers are done with their mission to find the historical female pilot. According to the AP, a separate group is planning its third voyage later this year, operating under a different theory. The group will be exploring the area near Howland Island, which was the destination Earhart and Noonan hoped to reach on their July 2, 1937 flight when they went missing.

Online search engine giant Google has shown its respect for the female pilot whose whereabouts are unknown by dedicating its daily Google Doodle on the website's homepage to Earhart.