Malaysia Airlines Flight 370 may have wrecked because of something as routine as a bathroom break. 

At least, that's according to Christine Negroni, an aviation-focused reporter and author of the recently published book, "The Crash Detectives: Investigating the World's Most Mysterious Air Disasters." In the book, which was released Sept. 27, Negroni posits that the MH370's journey turned fateful when Captain Zaharie Ahmad Shah left the cockpit for the restroom, the New York Post reported.

Shah put Fariq Abdul Hamid, a 27-year-old with 2,700 hours of experience, in charge while he took a "biological break" after takeoff.

"It's a long flight at cruise altitude, so there would have been no rush to get back to the flight deck," Negroni writes, according to an excerpt available on Google Books. "The tasks that First Officer Fariq had to take care of were routine. Easy peasy, as they say."

But when Shah left, Negroni theorizes, the cockpit depressurized. With wind throwing items into the air and his oxygen levels dropping, Fariq would have struggled to get help.

"The first officer would have realized immediately, 'This is an emergency,'" Negroni writes. "It would have been a neon light in his brain, but it would also have been competing with other lights and sounds, physiological sensations that had to have been both disconcerting and overwhelming."

Negroni has long been a proponent of the hypoxia theory, which suggests Fariq and Shah found themselves without oxygen due to cabin decompression. People with hypoxia may experience shortness of breath, extreme confusion and sweating, according to WebMD.

Because of this condition, the young pilot likely turned his transponder — or radio transmitter — to "standby" instead of sending out a call for aid. This basically powered the transponder off. Fariq may have tried to turn the plane back but failed due to his diminished capacity.

The plane was right between the Malaysian and Vietnamese airspaces, and because of that, MH370's disappearance may have been initially overlooked. "There could have been a five-minute delay before anyone noticed the plane hadn't arrived — a gap in which nobody pressed the alarm button," David Learmount, the safety editor for Flight International, told BBC News in 2014.

The rest is history.

MH370 and its 239 passengers vanished on March 8, 2014, and an exhaustive search of the Indian Ocean has turned up few results. In the past two years, only three pieces of debris have been definitively linked to the missing plane — and all three were discovered by amateurs.