HONOLULU (AP) — A $2.2 million expedition that hoped to find wreckage from 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 president of The International Group for Historic Aircraft Recovery tells The Associated Press the group still believes Earhart and her navigator crashed onto a reef off a remote island in the Pacific Ocean 75 years ago this month.

Pat Thrasher said Monday that the group has a significant amount of video and sonar data to pore over to look for things that may be tough to see at first glance.

Thrasher says the underwater environment with steep cliffs, caves and vegetation was tougher to navigate than searchers expected.

The U.S. State Department encouraged the privately-funded voyage.