Flight MH370 vanished on March 8 with 239 people, including two New Zealanders, aboard a flight from Kuala Lumpur to Beijing.
Malaysia said on Saturday it believed the plane had been diverted because its transponder and other communications devices had been manually turned off several minutes apart.
But there is confusion over the timeline of events before ground controllers lost contact with the aircraft.
Malaysia on Monday said it was the co-pilot Fariq Abdul Hamid who was the last person in the cockpit to speak to ground control.
Identifying the voice had been deemed crucial because officials initially said the words were spoken after one of the Boeing's two automated signalling systems - Aircraft Communications Addressing and Reporting System (ACARS) - had been manually disabled.
Read more from Herald reporter Lincoln Tan in Kuala Lumpur:
• Officials simulating lost jet's path
But Malaysia Airlines director Ahmad Jauhari Yahya contradicted that chronology, saying that the ACARS could have been switched off before or after Fariq spoke.
The Times said the changes made to the plane's direction through the Flight Management System were reported back to a maintenance base by ACARS, according to an American official.
This showed the reprogramming happened before the ACARS stopped working, at about the same time that oral radio contact was lost and the aeroplane's transponder also stopped. This fuels suspicions that foul play was involved in the plane's disappearance.
Investigators are scrutinising radar tapes from when the plane first departed Kuala Lumpur because they believe the tapes will show that after the plane first changed its course, it passed through several pre-established "waypoints'', which are like virtual mile markers in the sky, the Times said.
That would suggest the plane was under control of a knowledgeable pilot because passing through those points without using the computer would have been unlikely, it added.
Pilot 'a decent man'
Malaysian opposition leader Anwar Ibrahim has condemned speculation that the captain of the missing Malaysia Airlines plane - a member of Anwar's party - may have been driven by political motives to sabotage the plane.
Describing Captain Zaharie Ahmad Shah as a "decent man'', Anwar said he was "disgusted'' by what he saw as an attempt to smear the pilot and somehow implicate the opposition leadership in the March 8 disappearance of Malaysia Airlines Flight 370.
The investigative spotlight has focused on Zaharie and his co-pilot, Fariq Abdul Hamid, since it became clear that the plane was deliberately diverted from its intended flight path to Beijing by someone on board.
Multiple media reports have noted Zaharie, 53, was an active member of Anwar's Parti Keadilan Rakyat (People's Justice Party), and some have suggested he might have sabotaged the flight as an act of political revenge.
In a highly controversial case, Anwar was convicted of sodomy - illegal in Muslim Malaysia - just hours before MH370 took off.
"Is it a crime for anyone to be a member of Keadilan? To me it is an attempt to deflect the government's incompetence,'' Anwar said.
"I, of course, did not take the news reports seriously, but I am speaking out because I sympathise with the pilot and his family,'' he said.
"The mysterious disappearance of MH370 reflects not only an incompetent regime ruling the country, but an irresponsible government,'' he added.
The Malaysian authorities have had to defend themselves against repeated accusations that they withheld key information during the early stages of the search for the missing aircraft.
Video: Jet search expands with few clues
'No terrorist links'
Checks into the background of all the Chinese nationals on board the missing Malaysian jetliner have uncovered no links to terrorism, the Chinese ambassador in Kuala Lumpur said Tuesday.
The remarks will dampen speculation that Uighur separatists in far western Xinjiang province might have been involved with the disappearance of the Boeing 777 and its 239 passengers and crew early on March 8.
The plane was carrying 154 Chinese passengers when someone on board deliberately diverted it from its route to Beijing less than one hour into the flight. A massive search operation has yet to find any trace of the plane.
Chinese Ambassador to Malaysia Huang Huikang said background checks on Chinese nationals didn't uncover any evidence suggesting they were involved in hijacking or an act of terrorism against the plane, according to state news agency Xinhua.
Malaysian police are investigating the pilots and ground engineers of the plane, and have asked intelligence agencies from countries with passengers on board to carry out background checks on those passengers.
Malaysian authorities say that someone on board the flight switched off two vital pieces of communication equipment, allowing the plane to fly almost undetected. Satellite data shows it might have ended up somewhere in a giant arc stretching from Central Asia to the southern reaches of the Indian Ocean.
Huikang also said that Chinese authorities had begun searching for the plane on its territory.
Malaysian police say they are investigating the possibility of hijacking, sabotage, terrorism or issues related to the mental health of the pilots or anyone else on board, but have yet to give any update on what they have uncovered.
'There is always hope'
Officials revealed a new timeline Monday suggesting the final voice transmission from
the cockpit of the missing Malaysian plane may have occurred before any of its communications systems were disabled, adding more uncertainty about who aboard might have been to blame.
The search for Flight 370, which vanished early March 8 while flying from Kuala Lumpur to Beijing with 239 people on board, has now been expanded deep into the northern and southern hemispheres. Australian vessels scoured the southern Indian Ocean and China offered 21 of its satellites to help Malaysia in the unprecedented hunt.
With no wreckage found in one of the most puzzling aviation mysteries of all time, passengers' relatives have been left in an agonizing limbo.
Investigators say the Boeing 777 was deliberately diverted during its overnight flight and flew off-course for hours. They haven't ruled out hijacking, sabotage, or pilot suicide, and are checking the backgrounds of the 227 passengers and 12 crew members as well as the ground crew for personal problems, psychological issues or links to terrorists.
Malaysian defence Minister Hishammuddin Hussein said finding the plane was still the main focus, and he did not rule out that it might be discovered intact.
"The fact that there was no distress signal, no ransom notes, no parties claiming responsibility, there is always hope," Hishammuddin said at a news conference.
Malaysian Airlines CEO Ahmad Jauhari Yahya said an initial investigation indicated that the last words ground controllers heard from the plane "All right, good night" were spoken by the co-pilot, Fariq Abdul Hamid.
A voice other than that of Fariq or the pilot, Zaharie Ahmad Shah, would have been clearest indication yet of something amiss in the cockpit before the flight went off-course.
Malaysian officials said earlier that those words came after one of the jetliner's data communications systems the Aircraft Communications Addressing and Reporting System had been switched off, suggesting the voice from the cockpit may have been trying to deceive ground controllers.
However, Ahmad said that while the last data transmission from ACARS which gives plane performance and maintenance information came before that, it was still unclear at what point the system was switched off, making any implications of the timing murkier.
The new information opened the possibility that both ACARS and the plane's transponders, which make the plane visible to civilian air traffic controllers, were turned off at about the same time. It also suggests that the message delivered from the cockpit could have preceded any of the severed communications.
Turning off a transponder is easy and, in rare instances, there may be good reason to do so in flight for example, if it were reporting incorrect data.
The Malaysian plane does not appear to fit that scenario, said John Gadzinski, a 737 captain.
"There is a raised eyebrow, like Spock on Star Trek you just sit there and go, 'Why would anybody do that?"' Gadzinski said of what he is hearing among pilots.
Other pilots in the United States cautioned against reading too much into what little is known so far about the actions of the Malaysia Airlines crew.
"You can't take anything off the table until everything is on the table, and we don't even have an aircraft," said Boeing 737 pilot Mike Karn, president of the Coalition of Airline Pilots Associations.
Authorities have pointed to the shutdown of the transponders and the ACARS as evidence that someone with a detailed knowledge of the plane was involved. But Bob Coffman, an airline captain and former 777 pilot, said that kind of information is not hard to find in the digital age.
Authorities confiscated a flight simulator from the pilot's home Saturday and also visited the home of the co-pilot in what Malaysian police chief Khalid Abu Bakar initially said were the first police visits to those homes.
But the government, which has come under criticism abroad for missteps and foot-dragging in releasing information, issued a statement Monday contradicting that account, saying police first visited the pilots' homes as early as March 9, the day after the flight disappeared.
Coffman said the flight simulator could signify nothing more than the pilot's zeal for his job.
"There are people for whom flying is all consuming," he said, noting some pilots like to spend their off-duty hours on simulators at home, commenting on pilot blogs or playing fighter-pilot video games.
Although Malaysian authorities requested that all nations with citizens aboard the flight conduct background checks on them, it wasn't clear how thoroughly the checks were done in Malaysia. The father of a Malaysian aviation engineer aboard the plane said police had not approached anyone in the family about his 29-year-old son, Mohamad Khairul Amri Selamat, though he added that there was no reason to suspect him.
"It is impossible for him to be involved in something like this," said Selamat Omar, 60. "We are keeping our hopes high. I am praying hard that the plane didn't crash and that he will be back soon."
French investigators arriving in Kuala Lumpur to lend expertise from the two-year search for an Air France jet that crashed in the Atlantic Ocean in 2009 said they were able to rely on distress signals. But that vital tool is missing in the Malaysia Airlines mystery because the flight's communications were deliberately silenced ahead of its disappearance, investigators say.
"It's very different from the Air France case. The Malaysian situation is much more difficult," said Jean Paul Troadec, a special adviser to France's aviation accident investigation bureau.
Malaysia's government sent diplomatic cables to all countries in the search area, seeking more planes and ships and asking for any radar data that might help.
The search involves 26 countries and initially focused on seas on either side of Peninsular Malaysia, in the South China Sea and the Strait of Malacca.
The vast scope of the search was underlined when a US destroyer that already has helped cover 38,850 square kilometres of water dropped out.
The Navy concluded that long-range aircraft were more efficient in looking for the plane or its debris than the USS Kidd and its helicopters, so effective Tuesday the ship was leaving the Indian Ocean search area, said Navy Cmdr. William Marks, spokesman for the 7th Fleet. Navy P-3 and P-8 surveillance aircraft remain available, and can cover 38,850 square kilometres in a nine-hour flight.
Video: Jet will be found, says aviation expert
Over the weekend, Prime Minister Najib Razak said investigators determined that a satellite picked up a faint signal from the aircraft about 7 hours after takeoff. The signal indicated the plane would have been somewhere on a vast arc stretching from Kazakhstan in Central Asia to the southern reaches of the Indian Ocean.
The southern Indian Ocean is the world's third-deepest and one of the most remote stretches of water, with little radar coverage.
Hishammuddin said Monday that searches in both the northern and southern stretches of the arc had begun, and that countries from Australia in the south, China in the north and Kazakhstan in the west had joined the hunt.
Had the plane gone northwest to Central Asia, it would have crossed over countries with busy airspace. Some experts believe it more likely would have gone south, although Malaysian authorities are not ruling out the northern corridor and are eager for radar data that might confirm or rule out that route.
The northern corridor crosses through countries including China, India and Pakistan all of which have said they have no sign of the plane. China, where two-thirds of the passengers were from, is providing several planes and 21 satellites for the search, Premier Li Keqiang said in a statement.
"Factors involved in the incident continue to multiply, the area of search-and-rescue continues to broaden, and the level of difficulty increases, but as long as there is one thread of hope, we will continue an all-out effort," Li said.
Indonesia focused on Indian Ocean waters west of Sumatra, air force spokesman Rear Marshall Hadi Tjahjanto said.
Australia agreed to Malaysia's request to take the lead in searching the southern Indian Ocean with four Orion maritime planes that would be joined by New Zealand and US aircraft, Australian Prime Minister Tony Abbott said.
The Taliban theory
Meanwhile, The Independent has learnt that Malaysian authorities are seeking diplomatic permission to investigate a theory that the plane was flown to one of a number of Taliban strongholds on the border of Afghanistan and North West Pakistan.
At least 26 countries are now assisting in the search for the plane, intensifying challenges of co-ordinating ground, sea and aerial efforts. Countries known to be involved include Uzbekistan, Pakistan, Kyrgyzstan, Burma, Laos, Vietnam, Thailand, Indonesia and Australia, with special assistance regarding satellite data requested from the US, China and France. There have been no reported sightings or concrete leads on the whereabouts of the jet, which vanished from radar screens shortly after it took off in Kuala Lumpur at 00.40am on the morning of 8 March, destination Beijing.
The final confirmed location for MH370 on civilian radar was at 1.21am, but it was spotted less than an hour later on military radar, far to the west of that position. Malaysian Prime Minister Najib Razak revealed that "ping" signals from the plane was last received at 8.11am.
Last night sources in Kuala Lumpur assisting with the investigation told
The Independent
that full diplomatic permissions were being sought in order to rule out the theory that the plane could have flown to areas of Afghanistan and Pakistan that are not under government control.
Large areas of the southern half of Afghanistan are ruled by the Afghan Taliban, while some areas of north-west Pakistan, adjacent to or near to the Afghan border, are controlled by the Pakistani Taliban.
A spokesman for Malaysia Airlines said: "These are matters for the jurisdiction of those regions and Malaysia's armed forces and department of civil aviation. In regard to Pakistan and Afghanistan, we cannot explore those theories without permission. We hope to have that soon."
NZ Orion search area moved
A New Zealand Air Force P3 Orion has moved to Perth to continue the search for the missing Malaysian passenger plane.
"New Zealand is committed to playing our part in the international search effort for the missing MH370 flight. Our thoughts remain with the families who are waiting for news on their loved ones,'' said Defence Minister Jonathan Coleman.
"At the request of Malaysia, New Zealand's RNZAF P3 Orion will today relocate to the Royal Australian Air Force base Pearce, north of Perth, to join Australian, US and Chinese aircraft in the search effort of the southern corridor area, '' Dr Coleman said.
"The Air Force's upgraded P-3K2 Orion is an ideal option for search missions like this. It has state of the art sensors, can fly at low levels and remain airborne more than 12 hours.''
New Zealand sent an Orion to Malaysia last week after its Government accepted an offer from New Zealand to help with the international search.
- AP / UK Independent / AAP
