NBC NEWS -- Malaysia Airlines Flight 370 was deliberately diverted off course, authorities said Saturday, marking the biggest break in the investigation since the jet disappeared more than a week earlier with 239 people on board.
But the new information leaves questions unanswered and unearths new mysteries about a plane that vanished without apparent reason.
What led authorities to believe the plane veered off path due to "deliberate action by someone on the plane?"
Malaysia's Prime Minister Najib Razak said early Saturday that the aircraft's communications addressing and reporting system (ACAR) was disabled first, and then the aircraft's transponder was shut off before the flight turned around.
This was the first time that authorities shared that verified satellite "pings" indicated that the plane definitely switched course, although military radar suggested it was a strong possibility early on in the search.
"These movements are consistent with deliberate action by someone on the plane," Razak said.
It's possible to easily turn off the transponder and ACAR systems, but only if you know where to look. The transponder switch is located in the cockpit, and the the ACAR system is located on the lower level of the plane, said Tom Casey, a retired airline pilot who used to fly the giant Boeing 777.
"We pilots never go down there," Casey told NBC News. But a passenger could demand that a pilot shut the apparatus down, "and he would be able to confirm it because the system would go blank."
Why are Malaysian authorities being less-than-transparent?
Razak wouldn't explicitly say on Saturday that the plane was hijacked, and a Malaysian Airlines representative said from that point forward, all information on the missing plane would be released by Malaysian authorities. That announcement upset families of the missing passengers, witnesses reported, and the Malaysian government has been criticized by the Chinese for releasing only vague information.
"We understand the desperate need for information, but we have a responsibility to the investigation and the families to only release information that has been corroborated," Razak said during the Saturday briefing. The next scheduled press conference was abruptly canceled by Malaysian authorities.
The investigation into who took over the aircraft is active - police visited both the pilot and co-pilot's houses on Saturday - and officials might have to hold back information in order to properly execute the probe, NBC's Keir Simmons reported.
Who else will the Malaysian authorities focus their investigation on?
The investigation will examine everyone on the flight, including the passengers, said Razak. A Malaysian official said Friday that the first hour of Flight 370 would have been a prime opportunity to break into the cockpit. "If there were to be a real takeover, that would be the time when the crew will be moving in and out to serve the cockpit the drinks or refreshments," said Ismail Nasaruddin, president of the Malaysian National Union of Flight Attendants.
The plane severed communications with civilian air controllers at 1:20 a.m., just forty minutes after its 12:40 a.m. takeoff from Kuala Lumpur, according to The Associated Press.
Malaysian authorities are focusing on more than the pilots because if a pilot wanted to cease all correspondence with air traffic control, the pilot would also disable the satellite communication (SATCOM) system, which sent the "pings," Casey said.
"Someone with enough 'know-how' to intentionally deactivate communications capability had a serious lapse of that 'know-how' to forget to deactivate the one channel (SATCOM) that can communicate almost anywhere," John Ransom, a retired commercial pilot and safety consultant, told NBC News.
Malaysian Prime Minister Najib Razak, center, Malaysia's Minister for Transport Hishamuddin Hussein, left, and director general of the Malaysian Department of Civil Aviation, Azharuddin Abdul Rahman, delivers a statement to the media regarding the missing Malaysia Airlines jetliner MH370, on March 15, in Sepang, Malaysia. Najib said Saturday that investigators believe the missing Malaysian airliner's communications were deliberately disabled, that it turned back from its flight to Beijing and flew for more than seven hours.
Where is the search effort focused now?
The plane transmitted "raw satellite data" nearly seven hours after it lost touch with controllers on the ground, Razak said Saturday. This type of data doesn't reveal the exact location where the plane last lost contact, and given the amount of time the plane flew, search crews need to cover two huge "corridors" of land and sea, Razak said.
One corridor stretches north, across most of south Asia, and includes Afghanistan, Pakistan and India. In the opposite direction, a southern search spreads over Indonesia and the Indian Ocean.
"They're going to concentrate their efforts south," said Greg Feith, a former NTSB investigator, on TODAY Saturday. "If you're trying to stay out of radar view, then the best direction to go is to the south because you're going to be out over open ocean."
"I wouldn't be surprised if Australia doesn't eventually join this search process to assist," he added.
As of Saturday, 13 countries, including the United States, are aiding Malaysia with the search, which includes 43 ships and 58 aircraft, Razak said. Search efforts in the South China Sea - where the plane first lost contact and search efforts focused on earlier - had ended, Razak added.
What could the motive be?
While Casey stopped short of speculating the disappearance of the plane was the result of a terrorist attack, he said it could have been part of a larger "nefarious scheme."
"If you can do this three times, no one's going to get on an airplane," Casey said.
"I'm not convinced that this is suicide," Casey said, but both he and Ransom said no possibilities could be ruled out, and the reason the plane went down remains as much a mystery as its whereabouts.
"We may never know the absolute background, what was the fueling fire, if you will, for this person to take or commandeer the aircraft and do something with it," said Feith. "We may never find all the answers," he added.
The "very strange puzzle" is causing an international and "collective dread," Casey said. "We are addicted to information and we're not getting enough."
Copyright 2014 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.