Najprostsze wyjaśnienie jest zwykle tym trafnym....

A confidential document from the Malaysian police investigation into the disappearance of Malaysia Airlines Flight 370 shows that the plane’s captain, Zaharie Ahmad Shah, conducted a simulated flight deep into the remote southern Indian Ocean less than a month before the plane vanished under uncannily similar circumstances. The revelation, which Malaysia withheld from a lengthy public report on the investigation, is the strongest evidence yet that Zaharie made off with the plane in a premeditated act of mass murder-suicide.
Malaysian officials have suppressed at least one key piece of incriminating information. This is not entirely surprising: There is a history in aircraft investigations of national safety boards refusing to believe that their pilots could have intentionally crashed an aircraft full of passengers.

Shortly after Flight 370's disappearance, media reports revealed that Captain Zaharie Ahmad Shah's wife and three children moved out of his house the day before the disappearance; and a friend claimed that Captain Shah was seeing another woman and Shah's relationship with her was also in trouble. A fellow pilot and long-time associate of Shah stated the Captain was "terribly upset" that his marriage was falling apart. Police were also investigating reports that Shah received a two-minute phone call prior to the flight's departure from an unidentified woman using a mobile phone number obtained with a false identity. Furthermore, Captain Shah was also a supporter of Malaysian opposition politician Anwar Ibrahim, who was sentenced to jail on 7 March after an earlier acquittal on sodomy charges was overturned in a move viewed as politically motivated. Investigators noted strange behaviour by Shah from conducting 170 interviews—namely, that the Captain had made no social or professional plans for after 8 March, when Flight 370 disappeared. News reports about the Captain's lack of social plans and flight simulator exercises cite results of the police enquiry into the pilots, which have been shared with some of the investigation team but have not been released publicly. However, the police considered the possible culpability of all those onboard the plane, and identified the captain as the prime suspect—if it is proven human intervention was involved.

The United States' Federal Bureau of Investigation reconstructed the deleted data from Captain Shah's home flight simulator; a Malaysian government spokesman indicated that "nothing sinister" had been found on it. However, The Sunday Times later reported that among deleted flight paths performed on the flight simulator, investigators found a flight path into the Southern Ocean where a simulated landing was made on an island with a small runway. In 2016, a leaked American document stated that a route on the pilot's home flight simulator closely matching the projected flight over the Indian Ocean was found during the FBI analysis of the hard drive of the computer used for the flight simulator. This was later confirmed by the ATSB.

To take over the aircraft took "immense knowledge" and that even the co-pilot would not have been sufficiently skilled to disable the communications system and reprogramme a seven-hour flight off-course.

Former British Airways senior Boeing 777 pilot Simon Hardy told BBC News that the plane's route was "probably very accurate flying rather than just a coincidence", and noted that the aircraft's turn toward the north-west over the Malacca Strait allowed a clear view of the captain's home island of Penang. "Someone was looking at Penang. Someone was taking a long, emotional look at Penang. The captain was from the island of Penang. ... It does a strange hook... in order to look at [Penang] you have to turn left or right, get alongside it and then execute a long turn. If you look at the output from Malaysian 370, there were actually three turns, not one. Someone was looking at Penang."
In May 2018, Simon Hardy claimed on 60 Minutes Australia that the captain used the flight as a murder-suicide and had deliberately flown the plane over his hometown of Penang before turning right and ditching the plane over the Indian Ocean. He said they found these results by reconstructing the captain's flight plan from the military radar and that the captain had avoided detection of the plane by military radar by flying along the border of Malaysia and Thailand, crossing in and out of each country's airspaces.