Alternative theories
TIGHAR believes that the Niku hypothesis is the theory that best fits all of the facts of the case as known to date. Others disagree. TIGHAR has made a good-faith effort to take other theories into consideration and see how well they fit the facts of the case.
Splashed-and-Sank
This is the most intuitively appealing and a very reasonable theory. The official verdict was that the plane had probably gone down at sea and sunk without a trace. The supposed distress calls were declared to be either misunderstandings or outright hoaxes.
"Commander Walter K. Thompson decided fairly early that Earhart must have run out of fuel and that she landed the aircraft at sea shortly after the 08:43 (20:13 GMT) transmission received by Itasca."[1]
Near Howland Island
Elgen Long assumes that Earhart ran out of gas very shortly after the last transmission, relatively near to Howland Island.
Nauticos has made at least two deep-sea searches within the zone that Long calculates to be the most like region to find the downed aircraft.
After spying
There are a multitude of theories that Earhart and Noonan used the round-the-world flight as a cover story for spying on Japanese military installations in the Pacific en route to Howland Island.
The first version of this theory appeared in Flight for Freedom, a 1943 movie that showed a woman pilot and her navigator plunging into the ocean, sacrificing their lives in a noble attempt to glean valuable information about the Japanese military buildup in their Pacific territories.
Most of the "Captured by the Japanese" scenarios below are variants of this theory, although some may suppose that the Japanese captured Earhart and Noonan by accident and merely held them as prisoners of war on suspicion of spying.
Caught spying
Died on Saipan
Died on Tinian
Died on any number of Pacific Islands
Came home and hid in New Jersey
Crashed elsewhere
In the Gilbert Islands
In the Phoenix Islands
McKean
Winslow Reef
Christmas Island
Kanton Island
In 1998, a thirteen-person team investigated whether one of the Electra's engines had been helicoptered into Kanton (Canton) Island. No radial engine was found, though the dump was it was probably buried was located. Subsequent research among personnel who served on Kanton at the time and calculation of the fuel necessary to carry a radial engine from Nikumaroro to Kanton by helicopter ruled out the likelihood that the engine was from the Electra. In all likelihood, it was from an aircraft that crashed on Kanton itself.