Terrorism experts highlight court evidence of supergrass who talked of shoebomb.
Evidence of a plot by Malaysian Islamists to hijack a passenger jet in a terrorist attack copying 9/11 was being investigated in connection with the disappearance of Flight MH370.
An al-Qaeda supergrass told a court last week that four to five Malaysian men had been planning to take control of a plane, using a bomb hidden in a shoe to blow open the cockpit door.
Security experts said the evidence from a convicted British terrorist was "credible". The supergrass said that he had met the Malaysian jihadists - one of whom was a pilot - in Afghanistan and given them a shoe bomb to use to take control of an aircraft.
A British security source said: "These spectaculars take a long time in the planning."
The possibility of such a plot, hatched by the mastermind of the 9/11 attacks on the Twin Towers in New York, was bolstered by an admission on Saturday by Najib Razak, Malaysia's Prime Minister, that the Boeing 777's communications systems had been deliberately switched off "by someone on the plane".
It emerged that:
Flight MH370 had changed direction and altitude after communications devices had been deliberately disabled.
The plane flew for up to seven hours after civilian radar lost touch with it.
An unnamed official briefed that the plane had been hijacked although Najib refused to confirm that was the case.
The plane flew towards either Indonesia or to Kazakhstan after the transponder and messaging systems were disabled.
Police searched the homes of both pilots for two hours over concerns one may have switched off the communications systems in a suicide bid.
Chinese officials accused Malaysia of withholding information in a ratcheting up of diplomatic tensions between the two countries.
In evidence in a court case last Wednesday, Saajid Badat, a British-born Muslim from Gloucester, said that he had been instructed at a terrorist training camp in Afghanistan to give a shoe bomb to the Malaysians. Giving evidence at the trial in New York of Sulaiman Abu Ghaith, Osama bin Laden's son-in-law, Badat said: "I gave one of my shoes to the Malaysians. I think it was to access the cockpit."
Badat, who spoke via video link and is in hiding in the UK, said the Malaysian plot was being masterminded by Khalid Sheikh Mohammed, the principal architect of 9/11. According to Badat, Mohammed kept a list of the world's tallest buildings and crossed out New York's Twin Towers after the September 11, 2001 attacks with hijacked airliners as "a joke to make us laugh".
Badat told the court last week that he believed the Malaysians, including the pilot, were "ready to perform an act". During the meeting, the possibility was raised that the cockpit door might be locked. Badat told the court: "So I said, 'How about I give you one of my bombs to open a cockpit door?"'
The disclosure that Malaysians were plotting a 9/11-style attack raises the prospect that both pilots were overpowered and the plane intended for use as a fuel-filled bomb. One possible target, if the scenario is correct, will have been the Petronas Towers in Kuala Lumpur, a symbol of Malaysia's modernity and the world's tallest buildings from 1998 until 2004.
Badat, who was jailed for 13 years in 2005 for his part in a conspiracy with the "shoe bomber" Richard Reid to blow up a transatlantic jet, had given similar evidence in 2012. In other words, his claims were first made long before the disappearance of Flight MH370.
In the earlier case, during the trial of Adis Medunjanin, an American who was later convicted of conspiring to blow up New York subways, Badat told prosecutors of the Malaysian shoe bomb plot. Asked what he knew of the Malaysian group, he replied: "I learnt that they had a group, uh, ready to perform a similar hijacking to 9/11."
Asked if he helped them, he said: "I provided them with one of my shoes because both had been, uh, both had explosives inserted into them."
Professor Anthony Glees, director of the University of Buckingham's Centre for Security and Intelligence Studies, said the prospect of an Islamist plot offered one explanation for why the Malaysian authorities "have not been telling us the whole truth".
Glees said: "I believed this was a hijacking as soon as we were told that the plane had altered its flight path. Evidence that it turned back to Malaysia means that this could easily have been a Malaysian Islamist plot to turn the plane into a 9/11-style bomb to fly it into a building in Kuala Lumpur.
"Now we know there is evidence of a Malaysian terror cell with ambitions to carry out such an attack and so this makes it even more credible."
Glees added: "The global repercussions of another 9/11 attack, including grounded aircraft and stock markets crashes, is something no Government would want to face."
James Healy-Pratt, head of aviation at Stuarts Law solicitors, said the lack of information from Malaysian authorities was in stark contrast to the reaction of French officials when an Air France plane crashed in the Atlantic in 2009.
Healy-Pratt, who represented 50 families in the Air France crash, said: "Serious questions need to be asked about how this has taken a week to get so little information. If it is terrorism, that will have an effect on the Malaysian stock market and local economy."
Last May, two Malaysian men were arrested for links to al-Qaeda and charged with joining the Tanzim al-Qaeda Malaysia group. In a separate incident, two other men from Malaysia were held in Lebanon as they tried to cross into Syria to join Islamist extremists fighting the Assad regime.
In 2001, Yazid Sufaat, a biochemist and former army captain, was imprisoned for seven years under internal security laws on suspicion of being part of the Jemaah Islamiyah network, the terrorist organisation behind the Bali nightclub massacre, which killed 202 people in 2002. Yazid, who was released in 2008, was also suspected of providing lodging for two of the 9/11 hijackers.
Malaysian sources said Islamic terrorism carried out by Malaysian jihadists is unlikely since the country has only a tiny number of Muslim fundamentalists.
The mystery of MH370
John Hansman, an aeronautics professor at Massachusetts Institute of Technology, said that having gained access to the cockpit it would be possible for an intruder to turn off the transponders. But knowing how to shut down other systems would be more difficult. He said that even if hijackers got that far they would have found it difficult to keep flying, make a successful landing, and hide the plane. "If it was a hijacking, it was probably a hijacking gone bad."
Others believe that someone with a detailed knowledge of the plane could take it over and fly it while evading detection. Alan Diehl, a former crash investigator with the US National Transportation Safety Board, said intruders could get below radar systems and fly to an abandoned airstrip. "Even today, satellites don't cover every square kilometre of the Earth," he said.
Aviation consultant Chris Yates said: "It's increasingly clear that the hand of some form of terrorism is at play ... The levels of specialist aviation knowledge on display here cause me to cast my eyes back to 9/11, when hijackers had acquired a level of technical and flight training."
David Gleave, a former air crash investigator, said that any terrorist seizure of the plane would have required "one hell of a piece of planning".
Phil Giles, a former air safety investigator who worked on the Lockerbie bombing, said: "Unless the hijacker has a fair amount of technical and aviation knowledge, he would have to rely on putting a gun to the pilot's head".
Mike Glynn, a committee member of the Australian and International Pilots Association, thought pilot suicide was the most likely explanation for the disappearance. It was the suspected cause of a SilkAir crash flying from Singapore to Jakarta in 1997 and an EgyptAir flight in 1999. "A pilot rather than a hijacker is more likely to be able to switch off the communications equipment," Glynn said. "The last thing that I, as a pilot, want is suspicion to fall on the crew, but it's happened twice before."
Tony Cable, an investigator who worked for the UK Air Accidents Investigation Branch for 32 years, said: "The sensitivity of some of the military radar and satellite information is clearly posing a problem. I suspect there is an awful lot more information that is known but that is not being released."
Strobe Talbott, the president of the Brookings Institution, tweeted that "Malaysian plane mystery: Direction, fuel load & range now lead some to suspect hijackers planned a 9/11-type attack on an Indian city". He added: "Malaysian#370 as hijack: 1 of many theories. Speculation: hijackers headed toward India but crashed like UA#93 on 9/11". United Airlines Flight 93 was hijacked on September 11. It crashed in Pennsylvania during an attempt by some of the passengers to regain control, killing all 44 people on board.
- Independent, Observer, AP