One of the best-known Earhart historians, Long served as a consultant for the upcoming movie "Amelia" starring Hilary Swank, scheduled for release in October.
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"Ric Gillespie and the Tighar group have done a tremendous amount of research over many years, and have added much information to the knowledge of Earhart's last flight," Long wrote in an e-mail to ABCNews.com. "However, when world-recognized experts in aircraft performance (Dr. F.E.C. Culick, California Institute of Technology), and radio propagation experts (Thomas Vinson, Rod Blocksome and radio engineers at Collins Radio, Cedar Rapids, Iowa) analyzed the data they came to different conclusions than Tighar."
Long believes Earhart ran out of fuel shortly after 2013 GMT, July 2, 1937.
"She was then forced to ditch her plane into the ocean somewhere near Howland Island," he said. "No message or signals of any kind were ever verified as having really come from Earhart's plane after her last and only partly finished message to the Coast Guard Cutter Itasca at 2013 GMT."
To that, Gillespie said: That's what I used to think.
"What Elgen needs to explain is, who sent all those radio distress calls in the days following Earhart's disappearance? He'll say that the Coast Guard later proclaimed them to all be hoaxes and misunderstandings. That is true. It is also true that the Coast Guard had no basis for saying that," Gillespie said.
Gillespie carefully studied the nearly 200 possible radio messages that could have been from Earhart. Many of them were hoaxes, but Gillespie believes some of the calls, made days after she first disappeared, are credible.
"Either Earhart was on land somewhere south of Howard Island and North of Samoa or there was a hoaxer in that region who had the capability of sending signals on Earhart's frequency and could mimic Earhart's voice and information about Earhart that only Earhart and her closest associates could have known. These calls go on for days. They don't occur randomly over time, they occur at night and also at times when tide is low at the island where we think she landed."
So the debate continues, and so does the search for remnants of Earhart's plane. Ever since the U.S. government failed to find "Lady Lindy," as Earhart was known, during its $4 million exhaustive air and sea search, researchers have tried to piece the puzzle together.
Gillespie and his crew have searched the waters of the Pacific many times before, but this time they'll go much deeper, near a reef where they believe her plane crashed. His team's goal is to explore 1,000 feet beneath the ocean's surface.
"This location is right where the Navy thought she was when they were doing the search" at the time of her disappearance, he said.
The Tighar crew will include several volunteers, many of whom have gone on previous expeditions, and who have advanced degrees in the sciences.
"The volunteers are really bright people who are just fascinated by this mystery, and we are all motivated by the same thing ... and it is not to honor the memory of Amelia Earhart," said Gillespie, who has led nine expeditions searching for evidence of Earhart's demise over the past 20 years. "We are investigation junkies. We love the thrill of the search and scientific process."