The search for MH370 has ended. Here are the theories behind the plane's disappearance

Shelby Fleig | USA TODAY

Show Caption Hide Caption Mystery of flight MH370 crash solved? Investigators are claiming to have solved the mystery of a Malaysian airlines flight that vanished with 239 people on board. Veuer's Sam Berman has the full story.

Search efforts to find the Malaysia Airlines Flight 370 that mysteriously vanished more than four years ago have finally ended, leaving the world with only theories — for now — as to what happened to the aircraft.

American exploration company Ocean Infinity started an investigation for the Malaysian government in January and stopped looking for clues Tuesday.

The flight mysteriously vanished March 8, 2014, while en route from Kuala Lumpur to Beijing with 239 people on board. An official search of the southern Indian Ocean by Australia, Malaysia and China ended in January 2017.

Conspiracy theorists have tried to explain the mystery with tales of a hijacking, sudden fire and even aliens and black holes. But two main theories remain the most popular schools of thought for what happened to MH370:

It was a planned mass murder-suicide

60 Minutes Australia aired a panel discussion last week with aviation experts who concluded the MH370 pilot turned off tracking devices and depressurized the plane, knocking all passengers unconscious as he intentionally continued off course.

"He was killing himself,” said Canadian Air crash investigator Larry Vance on the program. “Unfortunately, he was killing everybody else on board, and he did it deliberately.”

In this theory, the veteran pilot Captain Zaharie Ahmad Shah turned the plane to fly around his hometown of Penang, Malaysia, then far out over the Indian Ocean before crashing into the water at a high speed.

Vance’s new book, MH370: Mystery Solved, claims that washed up plane parts support his theory that it crashed outside the original search area. Believers in this theory think Shah was depressed because his wife was divorcing him.

The pilot was unconscious as the plane veered off course and eventually ran out of fuel

The Australian Transport Safety Bureau, which led the initial investigation, contends MH370 flew off course and ran out of fuel as passengers and crew members were likely unconscious or dead inside the depressurized plane.

When Malaysian, Chinese and Australian government officials called off a three-year search last year, a final report determined no progress in finding a reason the plane went missing or where it crashed.

Peter Foley, who directed the Australian Transport Safety Bureau search, has disputed the claim that the pilot crashed intentionally. He has argued that even with an oxygen mask, nobody could have remained in control of a depressurized plane.

Contributing: The Associated Press