The disappearance of Malaysia Airlines flight MH370 may have been "an act of piracy" and the possibility that its hundreds of passengers are being held at an unknown location has not been ruled out, US investigators said last night (Friday).
Seven days after the Boeing 777 vanished en route to Beijing with 239 people on board, officials are examining the possibility the flight was deliberately steered off course and landed by an unknown hijacker.
There were claims yesterday that the plane flew on for more than five hours after it disappeared in the early hours of Saturday. In theory, MH370 could have flown more than 2,200 nautical miles, meaning it may have reached as far as the Indian border with Pakistan.
As an international fleet of more than 50 ships pushed further in to the Indian Ocean to search for signs of a crash, US and Malaysian investigators believe "human intervention" could have played a role in the disappearance.
US authorities think the aircraft continued to send faint transmissions, or "pings", for several hours after the flight was last in contact with the ground.
The pings, sent automatically by the 777's internal systems, raise the possibility that the flight was still airborne but that whoever was in control had deliberately severed contact with the ground.
Data from military satellites also suggest that the MH370 was flying over the west coast of Malaysia, hundreds of miles off its intended course north-east to China, Reuters reported, citing two sources close to the investigation. The military radar, more powerful than its civilian counterparts, suggests that the plane may have been following a series of established "way points" - geographic turning points used by pilots to navigate their course.
The flight reportedly disappeared off military radar as it flew north-west of Malaysia towards the Andaman and Nicobar Islands, an Indian territory made up of 572 small islands in the Indian Ocean.
Hishammuddin Hussein, the Malaysian transport and defence minister, refused to comment on the military radar reports but said his country was "following all leads". He said that police had not yet searched the home of Zaharie Ahmad Shah, the experienced Malaysia airlines captain of MH370.
The respected aviator built a personal flight simulator at his house on the edge of Kuala Lumpur, the Malaysian capital.
The hijacking theory is just one of many competing possibilities as investigators remain baffled how the airliner could have disappeared without trace.
While the naval search for the MH370 began in the Gulf of Thailand and the South China Sea, evidence that the flight remained airborne for hours after it was last seen has led to a massive expansion of the search grid.
A fleet of 57 ships from 13 different countries is now actively hunting through the vast expanse of the Indian Ocean, where the average depth is 13,000 feet - nearly 10 times deeper than the Gulf of Thailand.
The Indian navy is taking the lead on the land and water search around the Andaman Islands. The population of 380,000 is spread across only 37 of the islands, making it possible that the aircraft crashed on land without being noticed. Many of the islanders have little contact with the outside world and some of its tribes are considered among the most isolated people on the planet.
What happened to Malaysia Airlines flight MH370?
Tragically, one of the likely explanations for the missing airliner remains that the Boeing 777 suffered a catastrophic mechanical failure. Twenty minutes after take-off, the jet stopped transmitting its engine data. After another 23 minutes, all contact was lost. That would point to engine failure, a fire, or some other disaster.
Flaws: So far, rescuers have failed to find any debris at all in the region where the plane lost contact, despite a huge operation and shallow waters.
In this scenario, a crack in the plane leads to the cabin losing pressure and the passengers, flight attendants, and eventually the pilots losing consciousness from lack of oxygen. Meanwhile, the plane continues to fly on autopilot for several more hours.
Flaws: If the plane did not suffer an immediate catastrophe, there is no reason for the data transmission system and the plane's transponder, which sends its location, to be off while the autopilot functioned.
Terrorism was an early hypothesis, especially after it emerged that two men on board had been travelling on stolen passports. Later, it emerged that those men were more likely to be illegal immigrants.
Flaws: Ruling out the Chinese on board, who have no history of this type of terrorism, and the small number of passengers from other countries, there remains only a small number of Malaysians and Indonesians. Both countries have radical Muslim groups, but no one has claimed responsibility.
A scenario gaining currency is that the plane was hijacked. The timing of its disappearance, between two air traffic control zones, fits this theory, as does the radio silence. This would also explain why the mobile phones of some passengers were connecting, but not being answered.
Flaws: There has been no demand from hijackers, or contact from terrorists. The hijackers would have had to be trained to disable the communication and location systems, but police have not indicated anyone on the manifest with such skills.
If hijackers were not responsible, the pilots themselves could have taken over the plane. When Malaysian officials were asked about the flight simulator in Captain Zaharie Ahmed Shah's house, they visibly paled and stumbled. One of the pilots may have also wanted to commit suicide: there is a grisly precedent for pilots downing their planes in the ocean.
Flaws: Both men have been profiled by the police and no information has been released that suggests either was capable of such a deed.