Malaysia Flight MH370: 5 Likeliest Possibilities

More than a week after it disappeared, the whereabouts of MH370 are a mystery.

Malaysia Airlines flight MH370 has been missing since Saturday, March 8, and every new piece of information seems to shroud the flight's disappearance in more mystery.

Malaysian investigators now say deliberate action was taken to turn off communications systems and steer the aircraft far off course. "Pings" sent from the plane to a commercial satellite hours after MH370 disappeared suggest either a northern or southern route of flight, creating a search area that stretches from Kazakhstan into western China or from Indonesia into the southern Indian Ocean.

The mystery has spawned dozens of theories from experts and armchair analysts alike, all with varying degrees of credibility. Going on the information made public so far, there are only a few theories that fit - though none satisfactorily. Here are the remaining likely possibilities for flight MH370. [5 Real Hazards of Air Travel]

1. Pilot suicide MH370's transponder and its Aircraft Communications Addressing and Reporting System (ACARS) were both turned off shortly after the plane took off at 12:41 a.m. local time. There was a 14-minute gap between the last transmission of the ACARS and the last signal from the transponder, suggesting these systems were not destroyed by a sudden emergency.

Furthermore a voice, thought to be the plane's co-pilot Fariq Abdul Hamid, spoke to air traffic control in Malaysia after the ACARS turned off and just before the transponder turned off. The final message from the lost plane was a calm, "All right, good night." (Update at 7:59 a.m. ET on March 18: This timing is now in question, as Malaysian authorities now say they are unsure exactly when the ACARS switched off, but it was between 1:07 a.m. and 1:37 a.m.)

The plane then turned from its Beijing-bound route. A military satellite detected it west of the Malaysian peninsula at 2:15 a.m. local time.

"Based on the details surfaced so far, it seems to have been a very well-planned and performed operation," said David Cenciotti, a former Italian Air Force pilot and journalist, who blogs at TheAviationist.com.

The expertise required to conduct these maneuvers has investigators looking into the pilot and co-pilot, Capt. Zaharie Ahmad Shah, 53, and 1st Officer Fariq Ab Hamid, 27.

Theoretically, one of these men could have decided to commit suicide by airplane. Pilot suicide would be highly unusual, but not unprecedented. For example, U.S. investigators concluded that a 1999 crash near Nantucket, which killed all 217 people onboard EgyptAir Flight 990, was the result of the co-pilot deliberately flying the plane into the sea (Egyptian investigators dispute that finding).

Similarly, SilkAir Flight 185, which crashed in Sumatra in 1997, may have been a pilot suicide. There were no mechanical failures to explain why the plane went into a vertical dive, the U.S. National Transportation Safety Board concluded. The plane's trajectory could be explained by the captain's deliberate action, however. [Understanding the 10 Most Destructive Human Behaviors]

Something similar could have happened to Flight 370. But the explanation seems strange: Other pilots who have committed suicide-by-plane have aimed the nose at the ground and ended it quickly. MH370 flew for hours after contact was lost.

"Why would you take 200 other people with you, a logical individual would want to know?" said Gregory "Sid" McGuirk, a professor of air traffic control at Embry-Riddle Aeronautical University.

2. Pilot conspiracy Another theory holds that the pilots, or one of them, deliberately rerouted the plane for other reasons. This theory banks on the technical knowledge needed to change the plane's flight path, as well as suspicious circumstances around the flight's timing. [The 10 Craziest Conspiracy Theories]

Turning off the transponder and ACARS in the cockpit is as easy as flipping a switch and turning off a breaker, McGuirk told Live Science. The transponder, however, reportedly went off just as the plane was being handed off from Malaysian air traffic control to Vietnamese air traffic control.

Radar only has a radius of 150 to 200 miles (240 to 320 kilometers), McGuirk said. Over the continental United States, radar overlaps so there are no gaps. Over the ocean, however, there can be no ground-based antennas. Some countries, including India, also have gaps in their radar coverage, McGuirk said.

"If that's the case, then somebody knew exactly where the radar coverage gap was and decided to act at that moment," McGuirk said. "That's kind of far-fetched."

Still, the actions of the plane after the communications were turned off look deliberate, Cenciotti said. Programming the plane toward the navigational waypoints it appeared to be following wouldn't take too much expertise, he told Live Science. But the fact that the waypoints were so close to the edge of the Malaysian airspace boundary suggests they were deliberately chosen to obscure the plane's path.

"The farther to the radar, the harder to positively identify a so-called non-cooperative aircraft," Cenciotti said.

If one or both of the pilots did decide to reroute the plane, the motive they would have for doing so is unclear. Shah reportedly had strong political views and an at-home flight simulator; however, strong views do not necessarily suggest terrorism, and many pilots practice or play with flight simulators at home.

3. Terrorists Take Down Plane The pilots also may have been forced by terrorists aboard the plane to disconnect the communications and change course, before crashing somewhere. Alternatively, whoever commandeered the plane could have been an expert in aircraft and flown it themselves.

Authorities have not ruled out terrorism as a cause; no groups have come forward to claim responsibility or make demands, however. Sometimes terrorist groups do stay mum. For example, when Pan Am Flight 103 was destroyed by a bomb over Lockerbie, Scotland, investigators spent three years before issuing arrest warrants for two Libyan men. In fact, it wasn't until 2003 that Libyan leader Muammar Gaddafi admitted the country's role in the bombing. [Dictator Deaths: How 13 Notorious Leaders Died]

4. Terrorists stash the plane One possible explanation for why a terrorist group wouldn't claim responsibility for a hijacking: They plan to use the plane later.

The plane's northerly route may have taken it over remote areas where a Boeing 777 could potentially land - but landing a plane of that size without a functional runway would be difficult, particularly if the plane needs to fly again.

"It's very difficult to steal a 777 with Malaysian markings," McGuirk said. "It needs a 10,000-foot runway, so where are you going to put it down?"

Not to mention the eyebrows that would raise at a Malaysian airliner showing up where it shouldn't, McGuirk added.

If the plane flew north, which would give it a better chance of landing, it would have to fly over populated regions, making detection more likely. One far-out but not-impossible way to evade detection might be to "shadow" another plane, flying close so that both appeared to be the same object.

"It would be quite a difficult maneuver," Cenciotti said. "Let's not forget the entire maneuver, if performed, was performed at night, with no help from ground radars: Estimating reciprocal speeds, distances, altitudes based only on navigational lights is difficult. Maybe too much."

Beyond 9/11, there is precedent for the idea of stealing a plane for use in a later attack: In 1959, Brazilian Air Force officers hijacked a prop plane with 44 people aboard and landed it in southwest Brazil. They planned to use the plane in a bombing of Rio de Janeiro, but the plan fizzled and all hostages made it out of the ordeal alive. In 1994, Federal Express employee Auburn Calloway attempted to highjack a FedEx cargo jet for use in a suicide attack against the company's headquarters. The crew managed to overcome Calloway despite severe injuries. [9/11 Science: How Terrorist Attacks Rocked America]

Another plane, a Boeing 727-223, was driven off a runway in Angola in 2003. Aircraft mechanic Ben Charles Padilla and his employee John Mikel Mutantu were on the plane at the time, but it's not known whether they flew off in the aircraft or whether someone else killed them or took them hostage. The plane never reappeared, and the FBI closed the case in 2005.

5. Hijacking Gone Wrong MH370's disappearance could also be linked to a hijacking gone wrong. In 1996, Ethiopian Airlines Flight 961 crashed in the Indian Ocean after hijackers demanded it be flown to Australia. The plane only had enough fuel to make it to its destination in Nairobi, but the hijackers refused to believe the pilots.

The pilots first tried to stay near the African coast, knowing they could never make it to Australia. When the hijackers insisted they steer east, pilot Leul Abate instead flew toward the Comoro Islands off the east coast of Africa. There, as the plane ran out of fuel, the pilots tried for an emergency landing at the airport on Grande Comore, but an attack by the hijackers forced them to ditch in shallow water. All but 50 passengers died.

Something similar could have happened on Flight MH370. Perhaps hijackers forced the crew to turn back toward Malaysia as part of a 9/11-like attack. If the crew fought back and all aboard ended up incapacitated, the plane could have continued flying on autopilot until it ran out of fuel.

All of these scenarios are speculative. "It all comes down to, 'What's the motivation?'" said McGuirk, adding that there are more questions than answers at this point.

"I've never seen a situation like this, where none of the theories seem to fit," he said.

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This undated file photo from the internet shows a Malaysia Airlines' Boeing 777 passenger plane.

Jan. 20, 2012 -

As investigators try to figure out exactly what went wrong with the capsized cruise ship Costa Concordia off the Italian coast, maritime experts look back at historic maritime disasters so horrific they prompted new rules. "I like to say the laws and regulations are written in blood," said Kevin Gilheany, a consultant based in New Orleans who specializes in maritime safety compliance and spent 20 years in the U.S. Coast Guard. The past is full of tragedy at sea. Gilheany and other maritime experts highlighted these five deadly maritime disasters involving passenger vessels as ones that particularly shocked the public. Here, the MV Princess of the Stars is seen capsized off the coast of San Fernando, Romblon. The ship capsized at the height of Typhoon Fengshen on June 21, 2008. More than 800 people died in the accident.

The Heroes of the Concordia

The Medusa In July 1816, just about everything that could have gone wrong with the Medusa did. The French ship carrying around 400 people, mostly settlers bound for Senegal, ran aground far out at sea due to an incompetent captain. There weren’t enough lifeboats so a large but leaky raft was constructed from masts and rigging that the boats could tow ashore, said Charles Cushing, an expert who heads a naval architecture firm in New York City and teaches annuals course at the UN’s World Maritime University. Officers and politicians got in the boats while settlers and crew boarded the raft. One by one, each boat cut the lines and set off, leaving 146 people adrift. The sun quickly scorched many to death. Cannibalism and mutiny reigned. Only 15 survivors were eventually found alive. "It was a scandal of huge proportions," Cushing said. A graphic painting by the artist Théodore Géricault of the raft now displayed at the Louvre ensured the public would never forget.

General Slocum The Steamboat Inspection Service charged with safeguarding lives at sea had corrupt inspectors back in 1904 who let vessel owners get away with bringing a set of new lifejackets to a boat on the day of inspection and then removing them afterward, Kevin Gilheany said. On June 15 that year, the General Slocum was chartered by a Lutheran church in New York City for a trip to the Long Island shore. A fire broke out shortly after the ship carrying more than 1,300 left the pier. The captain didn't heed calls to stop and kept going, fanning the flames. Few aboard knew how to swim. When the passengers grabbed old lifejackets, the cork had disintegrated to powder but the vests were still weighted with iron, Cushing said. Many passengers were immigrants who didn’t know how to swim, Gilheany said. Adults put the lifejackets on children and threw them into the water, only to watch them sink. More than 1,000 passengers died. The captain was sent to prison and the disaster caused many reforms within the Inspections Service, which is now part of the U.S. Coast Guard. "I use that Slocum disaster in my training when I train captains to understand the legal liability they take on," Gilheany said.

How to Refloat a Capsized Liner

The RMS Titanic Speeding along for its maiden voyage from England to New York, the Titanic struck an iceberg the evening of April 14, 1912. Warnings about icebergs in the area had been ignored. The ship flooded and sank into the deep, killing 1,517. When word spread that the technologically advanced, "unsinkable" ship had gone down, the shock was immediate. Newspapers brimmed with news of the tragedy. There were so many Americans aboard the British ship that the U.S. Senate called for an immediate investigation. The British started their own inquiries as well. Out poured a host of regulations relating to adequate lifeboats, lifesaving equipment, and stability, Cushing said. An International Ice Patrol was formed, which still monitors icebergs to this day, and reports that no vessel heeding the patrol’s published iceberg limit has collided with one. "They fly the big C-130s," Gilheany said. "That's all because of the Titanic."

Wide Angle: Titanic Shipwreck 100 Years Later

The Moby Prince Outside of Italy, the Moby Prince is not that well known, said Giampiero Soncini, a former Italian Navy officer who heads SpecTec Group, which supplies specialized fleet management software. But the aftermath of the horrific disaster had the distinction of being filmed by an Italian TV crew. On April 10, 1991, the Moby Prince ferry collided with the oil tanker Agip Abruzzo in the Port of Livorno. The cause is still contended. Some blame fog, some say the rudder failed, and others say the crew was too busy watching a soccer match, Soncini said. The ferry caught fire and 140 aboard were either burned alive by the flames or asphyxiated on the toxic smoke. The mayday was too weak and miscommunication hampered rescue efforts. Only one man survived. "I happened to watched the live footage and it showed a body melted into the deck -- something I did not know was possible," Soncini said.

The Estonia Ferries that transport cars and trucks with decks close to the waterline are especially vulnerable to capsizing, Cushing said. He compares operating them to walking with a wide, shallow pan filled with water. Any inclination and the water rushes to one side. That "free surface" effect can be deadly. One night in late September 1994, a ferry called the Estonia filled with nearly 1,000 people was speeding along its route from Tallinn to Stockholm in rough, windy conditions. Suddenly the vessel rolled in enormous waves. Water rushed into the hold and the ferry capsized. Despite the convergence of rescue boats and helicopters, the frigid waters claimed more than 850 lives. One of the survivors told the New York Times she heard women screaming out in the sea. An official inspection later showed problems with locks on the bow door, and criticized the crew’s actions when metallic noises should have alerted them to serious problems. "It was the largest disaster in Europe since WWII and it shocked all of us,” Giampiero Soncini said. “Recent construction, good classification society, reputed company and yet more than 900 people died. In 1994!"

Scorned Cruise Ship Captain Not Alone in History