Conflict Specialist Larry Vance made the extraordinary claim after knocking out the investigators in order not to take him seriously.
Mr Vance, who wrote a book called MH370: Mystery Solved, told the Daily Star: "The passengers reached the South Indian Ocean and are deep in the deep in the sunken and intact fuselage."
The expert said he had proof of where the Boeing 777 fell, but added that it would not be taken seriously.
He said: "I sincerely believe that once the formal investigation team saw the physical data we discovered and how I interpreted them accurately, they would change their minds about what they thought happened to the MH370.
"Unfortunately, and disappointing, I was wrong."
Mr. Vance says he wrote his book in an attempt to give a "business account" of what happened and said it was his "duty" to do so.
The disappearance of the MH370 flight caused a number of theories after its disappearance in Beijing from Kuala Lumpur in March 2014, with 227 passengers and 12 crew members.
A popular theme for theories is government coverage, with many suggesting that the only explanation is that the CIA, the Russians, the Chinese or the Malaysians are responsible for the real reason for the disappearance of the flight.
Today's Malaysian Prime Minister, Mahathir Mohamad, confirmed this theory, indicating that US secret agents know where the plane is.
He said in 2014: "Someone is hiding something."
Another theory is a battery explosion or a mechanical failure.
There were more than two tonnes of lithium-ion batteries at the cargo dock, alongside more than four tons of mangosteen fruit.
Some scared juices from the fruit had leaked and come into contact with the batteries, causing an explosion.
A widespread theory is the air pressure in the cab decompressed and the life-saving oxygen masks were not working.
At an altitude of 35,000 ft, passengers would have had just 30 and 60 seconds before they dropped.
This theory could explain why they did not make calls from the cockpit or the passengers.
The MH370 pilot was the last voice to be heard before the plane disappeared, leaving some to believe that the responsibility was with him.
Captain Zaharie Ahmad Shah farewell to Kuala Lumpur's air control saying: "Goodnight, Malaysian three seven zero."
Two minutes later, the airplane's monitoring system was closed and some were associated with the removal.
This theory was rejected by the researchers.