A new theory based on the pilot's intent would mean the bulk of the wreckage from Malaysia Airlines flight MH370 is almost 3,500 miles north of the search's focus, a former National Transportation Safety Board investigator told Fox News Digital. 

Alan Diehl, who has over 30 years of experience investigating plane crashes, believes the missing Boeing 777 plummeted into the Andaman Sea, which is northwest of Malaysia.

The plane disappeared 10 years ago on Friday, on March 8, 2014. Diehl believes the pilot – Zaharie Ahmad Shah – wanted to make a political statement against the current regime "by commandeering the airplane, flying it clandestinely across Malaysia, taking it to the American military base in Diego Garcia, where he expected to broadcast his manifesto en route, land the plane and release the passengers."

There are countless theories with wide-ranging levels of plausibility, but Diehl's new idea – if true – would completely change the search efforts, which largely focused on the southern part of the Indian Ocean near the southwestern coast of Australia. 

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Ten years later, the only thing the 239 victims' families and friends can cling to are these theories – no matter how kooky some might be – because the reality is the governments involved have no definitive answers. 

It's still hard to fathom how a routine flight on March 8, 2014, from Kuala Lumpur, the Malaysian capital, to Beijing, China, veered off course after a series of bizarre, harsh turns, lost radar contact and then vanished. 

Diehl, a research psychologist who dedicated his life's work to recreating the pilot and crew's possible actions by analyzing their mental states, believes the turns and the plane's electronics going dark were intentional. 

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"This plane is electronically dark, and he (the pilot) probably turned off the lights too, and it's shooting across Thailand and Malaysia, in and out of the airspace," according to Diehl, who said it would have looked like nothing more than a "little blip" to radar operators, "if they were awake and diligent enough to see it."

There was a verbal message at 1:19 a.m. local time by the pilot to Malaysian air traffic: "Good night. Malaysian three-seven-zero." That was the last known communication but the systems were cut off.

Then the flight pattern went haywire. While air traffic control lost the plane, the Malaysian military radar was able to follow the aircraft, which showed it made unscheduled, sharp turns. 

Some believe the pilot was suicidal, and intended to make the plane disappear in one of the world's most remote spots, off Australia's southwest coast, where it's believed to have crashed. 

This theory involves the pilot locking his first officer – Fariq Abdul Hamid – out of the flight deck, cutting off all communications and depressurizing the aircraft until the passengers died of hypoxia, before plummeting into the ocean.  

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But information in the public domain doesn't suggest any motive for a suicide mission, Diehl said, and there's a way for the first officer to get back into the cabin by going through the electronics bay.

The official report, which was released in 2018, said, "There was no known history of apathy, anxiety, or irritability. There were no significant changes in his lifestyle, interpersonal conflict or family stresses."

"So that really doesn't fit," Diehl said, but he didn't dismiss the idea that the first officer was locked out.

If he wanted to disappear, Diehl believes he would have flown in the opposite direction toward the Mariana Trench, an oceanic trench in the Pacific Ocean that's over a mile farther from sea level than the peak of Mount Everest and about 1,580 miles long and over 40 miles wide. 

"That tells me he didn't want to disappear," Diehl said. 

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Another theory that garnered a lot of attention was an idea that the pilot, a known activist, wanted to embarrass the country's regime, and was shot down before he could execute a 9/11-style suicide flight into Beijing's Tiananmen Square. 

That target would have been en route, so he would not have had to make that sharp left turn, Diehl said, "which leads me to my theory that he wanted to make a political statement, nothing more, but something happened to the aircraft."

There are countless other wild ideas, like the pilot made a "D.B. Cooper" type hijacking and jumped out of a plane to meet a lover. Of course, there are alien and black hole conspiracies. 

"During all this initial hoopla several of these theories seem credible," Diehl wrote in his book, "Best Laid Plans."

"For example, a cargo fire may have occurred, or a passenger or stowaway may have hijacked the jet.

"While others seemed bizarre, like the idea that the CIA had it shot down because U.S. computer experts were aboard and might be defecting to China, or that erstwhile KGB agents electronically took control of the aircraft and flew it to an abandoned cosmodrome in the former Soviet Union."

Diehl dives deeper into his theory in his new book, "Best Laid Plans," which introduces his theory while using fictional characters and dialogue, except for the pilot and the first officer. 

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He presents a fictional – but plausible theory – that the first officer was purposely locked out, so he wouldn't be involved in the pilot's conspiracy to make a political statement, Diehl told Fox News Digital. 

But the first officer knew he could reopen the cockpit by going through a hidden trap door that leads to the E&E (electronics and equipment) bay, an area of "electronic racks and black boxes, with spaghetti-like wire bundles running everywhere," according to Diehl's book. 

While in the E&E bay, the pilot may have made a sharp turn, which could have created disaster as he tried to brace himself. 

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"With all the high voltage in there, if he bumped something, he could've started a fire accidentally, probably killing himself and causing a major problem," Diehl said. "The plane would've filled with smoke and probably burned a hole in the fuselage … and at 35,000 feet that would have caused an explosive decompression.

"And the rest, as they say, is history."

Diehl looked at the history of the Boeing 777 itself, which he called a "safe aircraft," but there have been high-profile crashes involving fires in the E&E bay. 

The search for the vanishing plane covered more than 2 million square nautical miles and focused on an area off the coast of Australia. 

The underwater search was officially called off in January 2017 after the Australian, Malaysia and Chinese governments scoured nearly 50,000 square miles of the Indian Ocean floor, which reportedly cost about $150 million. 

In January 2018, the Malaysian government began its partnership with a private contractor called Ocean Infinity, which is still involved.

Since the 2014 crash, pieces of debris were found along the coasts of South Africa and on the islands of Madagascar, Mauritius, Réunion and Rodrigues.

If Diehl's theory is right, and the plane was headed for the U.S. military base in Diego Garcia, the search, he said, should be focused in the Andaman Sea near Malaysia. 

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"Right now, I think they're basing the search on the assumption either the pilot was suicidal and wanted to fly as far as he could, seeping into the Indian Ocean by staying high and getting the best fuel economy and the greatest range or that the autopilot was set on high altitude," Diehl told Fox News Digital. 

"I don't think either theories are correct … We know that somebody was alive at 2:25 a.m. (local time) and they took into the Indian Ocean, and when the sun came up at 7 a.m., they would've discovered that they needed to head to the east to get to Indonesia or Australia, but they ran out of fuel."

That's why Diehl believes a "far more fertile area" to search would be along the eastern edge of the 2,500-mile "Seventh Arc."

The greatest air disaster mystery will likely remain unsolved without the wreckage, Diehl said. 

"That's the Rosetta Stone that will make this clear. That's the single biggest piece of evidence," he said. "And until they start looking again, and maybe not, maybe but also look at that Eastern end like they've been advocating."

Malaysian officials said earlier this week that the government was going to discuss a new search operation after being approached by Ocean Infinity. 

Oliver Plunkett, the chief executive of Ocean Infinity, said in a statement to news outlets that the company has been analyzing data to narrow the search area since the first go around. 

"This search is arguably the most challenging, and indeed pertinent one out there," he said. "We’ve been working with many experts, some outside of Ocean Infinity, to continue analyzing the data in the hope of narrowing the search area down to one in which success becomes potentially achievable."

Diehl said he hopes by putting out this book – with a new theory – that it will accomplish two things. 

"One, I want the Malaysian government to sign the f------ contract. And two, to say, you know, maybe this other theory about the Eastern Arc is something, and maybe get guys out there too."

At the end of Diehl's book, he wrote, "What happened after the aircraft disappeared was the largest, most expensive and protracted aviation search effort ever undertaken. One which, unfortunately, has yet to discover the location of the Malaysian jet’s wreckage."

Fox News Digital's Brooke Curto contributed to this report.