On the 75th anniversary of the disappearance of Amelia Earhart, competition to solve the mystery has reached fever pitch.

Two parties with diverging theories hope to lay to rest later this year the issue of what happened July 2, 1937, when Earhart and navigator Fred Noonan disappeared.

Jon Thompson says he will be the sonar operator this fall, when an expedition headed by David Jourdan and the deep-sea exploration company Nauticos begins a third mission to search near Earhart’s destination, Howland Island. They will search depths of 18,000 feet.

In July, Ric Gillespie, a longtime Earhart seeker, heads to an island where he believes they may have survived for a short time. He has a photo analyzed by the U.S. State Department that appears to show a landing gear.