KUALA LUMPUR, Malaysia -- The search for the missing Malaysian jetliner expanded east and west on Friday after American officials said it was emitting signals to satellites for hours after its last contact with air traffic control nearly a week ago over the South China Sea.
Malaysian officials insisted that investigators had yet to reach a definitive conclusion on what radar and satellite data showed, and said the search was being expanded because efforts in current areas have not found any wreckage from the Boeing 777.
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The possibility that the plane, carrying 239 people, flew many hundreds of miles (kilometers) beyond its last known location without any contact with the ground has strengthened speculation that its transponders and other communication devices were turned off deliberately.
That opens the possibility that one of the pilots, or someone with flying experience, wanted to hijack the plane for some later purpose, kidnap the passengers or commit suicide by plunging the aircraft into the sea.
Given the amount of fuel it had on board, the plane could in theory have reached anywhere in a large swath of South and Southeast Asia. In the absence of more information on its movements, finding it could be a massive task.
Malaysian Transport Minister Hishammuddin Hussein said the search was expanding further afield into the eastern stretches of the South China Sea and on the western side of the Malay Peninsula, northwest into the Andaman Sea and further into the Indian Ocean.
Beijing-bound Malaysia Airlines flight MH370 last communicated with air traffic base stations east of Malaysia in the South China Sea, which initially was the focus of the search. The theory that the plane turned back and flew west has been strengthened because Malaysia says it has military radar records showing unidentified blips that could indicate the plane doing this.
"I will be the most happiest person if we can actually confirm that it is the MH370, then we can move all assets from the South China Sea to the Strait of Malacca," Hishammuddin said.
India said it was searching hundreds of small, uninhabited islands in the Andaman Sea more than 1,200 kilometers (745 miles) to the west of the plane's last known position. Spokesman Col. Harmit Singh of India's Tri-Services Command said it began land searches after sweeping seas to the north, east and south of the Andaman and Nicobar Islands.
Malaysian officials declined to discuss when -- or even whether -- they had information about signals to satellites, and said they would release details only when they were verified.
"I hope within a couple of days to have something conclusive," Hishammuddin told a news conference.
A team of five U.S. officials with air traffic control and radar expertise -- three from the U.S. National Transportation Safety Board and two from the Federal Aviation Administration -- has been in Kuala Lumpur since Monday to assist Malaysia with the investigation.
If the plane had disintegrated during flight or suffered some other catastrophic failure, all signals -- pings to satellites, data messages and the transponder -- would be expected to stop at the same time. Experts say a pilot or passengers with technical expertise might have switched off the transponder in the hope of flying undetected.
No theory, however, has been ruled out in one of modern aviation's most puzzling mysteries.
Malaysia has faced accusations it isn't sharing all its information or suspicions about the plane's final movements. It insists it is being open, and says it can only narrow the focus of the search when there is undeniable evidence of the plane's flight path.
The White House said the U.S. may be drawn into a new phase of the search in the vast Indian Ocean but did not offer details. The U.S. Navy's 7th Fleet said it was moving one of its ships, the USS Kidd, into the Strait of Malacca.
A U.S. official told The Associated Press that the plane remained airborne after losing contact with air traffic controllers because it was sending a signal to establish contact with a satellite.
Boeing offers a satellite service that can receive a stream of data on how an aircraft is functioning during flight and relay the information to the plane's home base. The idea is to provide information before the plane lands on whether maintenance work or repairs are needed.
Malaysia Airlines didn't subscribe to that service, but the plane still had the capability to connect with the satellite and was automatically sending signals, or pings, said the U.S. official, who spoke on condition of anonymity because he wasn't authorized to discuss the situation by name.
Boeing has not commented.
Messages involving a different data service also were received from the airliner for a short time after the plane's transponder -- used to identify the plane to civilian aviation authorities -- went silent, the U.S. official said.
Hishammuddin said Malaysia was asking for radar data from India and other neighboring countries to see if they could trace the plane flying northwest. There was no word Friday that any other country had such details on the plane, and they may not exist.
In Thailand, secondary radar, which requires a signal from aircraft, runs 24 hours a day, but primary surveillance radar, which requires no signal, ordinarily shuts down at night at some locations, said a Royal Thai Air Force officer who asked not to be named because he was not authorized to talk to the media on the issue.
Air Marshal Vinod Patni, a retired Indian air force officer and a defense expert, said radar facilities in the Andaman and Nicobar Islands area don't work around the clock, either.
Mike Glynn, a committee member of the Australian and International Pilots Association, said he considers pilot suicide to be the most likely explanation for the disappearance, as was suspected in a SilkAir crash during a flight from Singapore to Jakarta in 1997 and an EgyptAir flight from Los Angeles to Cairo 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."
Glynn said a pilot may have sought to fly the plane into the Indian Ocean to reduce the chances of recovering data recorders, and to conceal the cause of the disaster.
Experts said that if the plane crashed into the ocean, some debris should be floating even if most of the jet is submerged. Past experience shows that finding the wreckage can take weeks or even longer, especially if the location of the plane is in doubt.