WASHINGTON — The first turn to the west that diverted the missing Malaysia Airlines plane from its planned flight path from Kuala Lumpur to Beijing was carried out through a computer system that was most likely programmed by someone in the plane’s cockpit who was knowledgeable about airplane systems, according to senior US officials.
Instead of manually operating the plane’s controls, whoever altered Flight 370’s path typed seven or eight keystrokes into a computer on a knee-high pedestal between the captain and the first officer, according to officials. The Flight Management System, as the computer is known, directs the plane from point to point specified in the flight plan submitted before each flight. It is not clear whether the plane’s path was reprogrammed before or after it took off.
The fact that the turn away from Beijing was programmed into the computer has reinforced the belief of investigators — first voiced by Malaysian officials — that the plane was deliberately diverted and that foul play was involved. It has also increased their focus on the plane’s captain and first officer.
Prime Minister Najib Razak of Malaysia told reporters Saturday that his government believed the plane had been diverted, because its transponder and other communications devices had been manually turned off several minutes apart. US officials were told of the new information over the weekend.
But Malaysian authorities on Monday reversed themselves on the sequence of events they believe took place on the plane in the crucial minutes before ground controllers lost contact with it early March 8. They said it was the plane’s first officer — the copilot — who was the last person in the cockpit to speak to ground control. And they withdrew their assertion that another automated system on the plane called Aircraft Communications Addressing and Reporting System had been disabled before he spoke.
Flight 370’s Flight Management System reported its status to the system, which in turn transmitted information back to a maintenance base, according to a US official. This shows that the reprogramming happened before the reporting system stopped working. The reporting system ceased to function about the same time oral radio contact was lost and the airplane’s transponder also stopped, fueling suspicions that foul play was involved in the plane’s disappearance.
Investigators are scrutinizing radar tapes from when the plane departed Kuala Lumpur because they believe the tapes would show that after the plane first changed its course, it passed through several preestablished “waypoints,” which are like virtual mile markers in the sky. That would suggest the plane was under control of a knowledgeable pilot, because passing through those points without using the computer would have been unlikely.
According to investigators, it appears a waypoint was added to the planned route. Pilots do that if air traffic controllers tell them to take a different route, to avoid weather or traffic. But in this case, the waypoint was far off the path to Beijing.
Whoever changed the plane’s course would have had to be familiar with Boeing aircraft, though not necessarily the 777 — the type of plane that disappeared. US officials and aviation experts said it was far-fetched to believe that a passenger could have reprogrammed the Flight Management System.
Normal procedure is to key in a five-letter code — gibberish to nonaviators — that is the name of a waypoint. A normal flight plan consists of a series of such waypoints, ending in the destination airport. For an ordinary flight, waypoints can be entered manually or uploaded into the Flight Management System by the airline.
One of the pilots keys in a waypoint on a separate screen known as a scratchpad, and after confirming that it has no typographical errors, pushes another button to move it into the sequence in the flight plan. Normal practice is to orally confirm the waypoint with the other pilot, then push another button to instruct the airplane to go there. With the change in course, the plane would bank at a comfortable angle, around 20 degrees, and make the turn. Passengers would not feel anything unusual.
ABC News reported Sunday the programmed turn had led investigators to believe it was being controlled by the pilot or hijackers.
One US safety expert, John Cox, a former airline union safety official, said someone taking such pains to divert the plane does not fit the pattern of past cases when pilots intentionally crashed and killed everyone on board.
“There’s an inconsistency in what we’ve seen historically,” he said, comparing the disappearance of Flight 370 with two murder-suicides, of an Egyptair flight off Nantucket Island in 1999 and a SilkAir jet in Indonesia in 1997. In those crashes, he said, the pilot involved simply pushed the nose of the plane down and flew into the water. The authorities searched the homes of the pilots in Kuala Lumpur on Saturday, seizing a flight simulator that one of them had in his home.
In an effort to determine whether the pilot had practiced taking down the plane, the authorities have reassembled the simulator for experts to examine. As of Monday night, US investigators had not been given access to the simulator or other electronic materials seized.
In another development, China’s state news agency on Tuesday said background checks on all its nationals on board the jetliner have uncovered no links to terrorism, the Associated Press reported.