(AP) HONOLULU - A $2.2 million expedition that hoped to find wreckage from famed aviator Amelia Earhart's final flight is on its way back to Hawaii without the dramatic, conclusive plane images searchers were hoping to attain.
But the group leading the search, The International Group for Historic Aircraft Recovery, still believes Earhart and her navigator crashed onto a reef off a remote island in the Pacific Ocean 75 years ago this month, its president told The Associated Press on Monday.
"This is just sort of the way things are in this world," TIGHAR president Pat Thrasher said. "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."
Thrasher said the group collected a significant amount of video and sonar data, which searchers will pore over on the return voyage to Hawaii this week and afterward to look for things that may be tough to see at first glance.
The group is also planning a voyage for next year to scour the land where it's believed Earhart survived a short while after the crash, Thrasher said.
Thrasher maintained touch throughout the search with TIGHAR founder Ric Gillespie, her husband, and posted updates about the trip to the group's website. The updates tell of a search that was cut short because of treacherous underwater terrain and repeated, unexpected equipment mishaps that caused delays and left the group with only five days of search time rather than 10, as originally planned.
During one episode, an autonomous underwater vehicle the group was using in its search wedged itself into a narrow cave, a day after squashing its nose cone against the ocean floor. It needed to be rescued.
"The rescue mission was successful - but it was a real cliffhanger," Gillespie wrote in an email posted online 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."
Thrasher said the environment was tougher to navigate than searchers expected.
The U.S. State Department had encouraged the privately-funded voyage, which launched earlier this month from Honolulu using 30,000 pounds (13,608 kilograms) in specialized equipment and a University of Hawaii ship normally used for ocean research.
The group's thesis is based on the idea that Earhart and navigator Fred Noonan landed on a reef near the Kiribati atoll of Nikumaroro, then survived a short time.
Previous visits to the island have recovered artifacts that could have belonged to Earhart and Noonan, and experts say an October 1937 photo of the shoreline of the island could include a blurry image of the strut and wheel of a Lockheed Electra landing gear.
The photo was enough for the State Department blessing, and led to the Kiribati government to sign a contract with the group to work together if anything is found, Gillespie said at the start of the voyage.
A separate group working under a different theory plans its third voyage later this year near Howland Island.
Earhart and Noonan were flying from New Guinea to Howland Island when they went missing July 2, 1937, during Earhart's bid to become the first woman to circumnavigate the globe.
Learn more about the International Group for Historic Aircraft Recovery and their mission in the video below