KUALA LUMPUR, Malaysia - 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, relatives of those on the Boeing 777 have been left in an agonizing limbo. Experts can only estimate that the plane's final location is along one of two corridors stretching toward the north and toward the south.
The two corridors represent the possible path of the plane based on the last signal that was picked up by a satellite over the Indian Ocean, CBS News reported. The size of the new search areas -- 7 million square miles - is based on estimates of the jetliner's remaining fuel.
To the north, the plane would have flown mostly over land. China and Kazakhstan are now checking their radar records.
The Australians are leading the search in the south, mostly over water.
Malaysian Defense 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 heard from the plane by ground controllers - "All right, good night" - were spoken by the co-pilot, Fariq Abdul Hamid. Had it been a voice other than that of Fariq or the pilot, Zaharie Ahmad Shah, it would have 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.
Airline 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 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 probably available on the Internet.
"We really don't know what happened in the airplane at this point," he said.
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 they were doing such checks at home. 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. "He is a good boy. ... 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 for the search, as well as to ask 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 U.S. destroyer that already has helped cover 15,000 square miles of water dropped out.
The Navy determined 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 15,000 square miles in a nine-hour flight.