The UnXplained: What REALLY Happened to Malaysia Airlines Flight 370? (Special)

SHATNER: Malaysia Airlines Flight MH370 prepares to depart from Kuala Lumpur International Airport, en route to Beijing. On board are 227 passengers and a flight crew of 12. NANCE: Malaysia 370 was a commercial flight.

Malaysia Airlines, it was a routine procedure, a routine flight as we say. The flight path was more or less a straight line. Aimed from Kuala Lumpur out over the water in the South China Sea to the main landfall of China.

As far as everybody was concerned, it took off normally, was flying its route north towards China. TUTTLE: Then all of a sudden it turned off its communications and basically went dark. SHATNER: At about 1:20 a.

m. , as the plane was flying over the South China Sea, ground control lost all contact with the plane. One second, the 240-ton Boeing aircraft was emitting a clear transponder signal to air traffic control.

And then, mere moments later, there was nothing. The fact that the signal disappeared, that was the unusual element. The fact that that transponder, which was chirping back every time it was hit by the radar beam from air traffic control, went silent.

KAKU: Flight controllers frantically tried to communicate with the airplane. Nothing. What happened?

How can you lose a jetliner? How can it vanish in thin air? SHATNER: Although the aircraft was lost on civilian radar screens, unbeknownst to ground control, military radar was able to track the plane for another hour.

And what it detected was baffling. At that point, when the radios were turned off, the flightpath did a 90-degree turn to the left, basically on a southwestern heading and disappeared into the vastness of the Indian Ocean. We don't know the motivation for doing this.

We just, we don't know. SHATNER: Around 2:20 a. m.

, radar contact with the plane was lost for good. By 7:20 a. m.

, one hour after it was scheduled to land, authorities in Beijing realized that Flight MH370 was not going to reach its destination. A search and rescue operation was immediately launched and it quickly became the most expensive and difficult in aviation history. The initial search was basically, uh, aircraft searching for the immediate wreck, looking for any survivors or telltale wreckage on the sea surface.

Unfortunately, after a while, things sink. Survivors aren't there and you go from a search and rescue mission to a search and recovery mission. SHATNER: When the wreckage did not turn up, officials were eventually forced to admit that all 239 people on board the flight had perished.

We were clueless as to what could have caused this tragedy right under our noses. In an era when we have the Internet, satellite, radar communication, it just disappears off the radar screen. SHATNER: The wreckage of the plane, despite the efforts of the world's top aviation experts had seemingly vanished without a trace.

But then after months of searching, investigators finally uncovered an important clue. Boeing had included a maintenance reporting thing that goes by satellite. It was called an ACAR system.

And Boeing had installed the system to report maintenance information about the engines in the airplane every hour. In this particular case, it was still pinging away. It was saying essentially to the satellite, "Hey, I'm here.

You want any information? " SHATNER: The information revealed by the ACAR system was shocking. It showed that the plane did not crash anywhere near where it was last detected.

It actually changed course and kept on flying. GREG LIEFER: It was flown for another six hours after it made the initial diversion from its intended flight plan and it was flown, uh, to a very remote area. SHATNER: Based off this data, aviation experts believe that the plane most likely crashed somewhere in the southern portion of the Indian Ocean after running out of fuel.

It seems that the aircraft flew in the wrong direction for thousands of miles, to a distant part of the ocean where there was no possible place to land. But how could that have happened? Initially, the theory that was proposed by a lot of the media was that the pilot in command committed suicide.

But in fact, the accident report clearly stated that the pilot had no history of emotional or physical problems that would preclude suicide and family, friends and coworkers said he had no abnormal behavior before the flight. KAKU: Other people say, "No, it was some kind of mechanical failure. " If it were to catch on fire, the plane could rapidly depressurize, meaning that people would suffocate very rapidly.

And I think that what happened then was you had a ghost airplane. Where everyone was either dead or dying. It was randomly going back and forth until it finally ran out of fuel and crashed into the Indian Ocean.

You had theories of oxygen malfunction that incapacitated the pilots but I don't think that makes sense because the aircraft, it certainly appeared to me, like it was being flown manually for up to at least 30 minutes, if not up to an hour after it made that hard left turn. The thing that makes the most sense to me was some type of hijacking. The abrupt maneuvers that it was making, the changes in altitude and air speed and heading, all that indicates to me that it was a deliberate, uh, manipulation by other people that took control of the aircraft.

But then that poses the question, "Well, why did they hijack the aircraft? What was the motive and why fly to the southern Indian Ocean? " SHATNER: While the theory that the plane was hijacked may sound logical, authorities thoroughly checked the background of all the passengers and crew and none of them fit the profile of a hijacker.

The truth is that while several of the explanations that have been put forth seem to have merit, we simply don't have enough information to verify any of them. We have no way of knowing because the cockpit voice recorder is at the bottom of the Indian Ocean someplace. But the other, and the most important thing to keep in mind is, we found a piece of that airplane.

A piece of the wing was found and verified. It was washed up on, I believe the shores of Madagascar. Or close to it.

And it was definitively from this particular airplane. So, we knew then categorically that that airplane had gone into the Indian Ocean. And in this case, this particular piece of the plane had taken about a year and a half to float all the way across the Indian Ocean.

LIEFER: It was one of 27 pieces that were eventually recovered and it was one of three pieces out of the 27 that was positively identified as coming from the aircraft. The aircraft wasn't found, occupants weren't found, but yet, 17 months later, they find these pieces of debris, thousands of miles away. And that's what makes this mystery, I think, probably the biggest mystery of all the aviation mysteries.