Missing Malaysian Plane Update: Search area goes from 'chessboard to football field.

The more time that passes, the wider the search area for the missing Malaysia Airlines Flight 370 becomes.

After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, efforts are now expanding west into the vastness of the Indian Ocean.

"It's a completely new game now," Cmdr. William Marks of the U.S. 7th Fleet, which is helping in the search, told CNN, describing the situation. "We went from a chess board to a football field."

USS Kidd, a destroyer from the U.S. Pacific Fleet, is being moved into the Indian Ocean to begin searching that area at the request of the Malaysian government, Marks said.

The broadening scale of the search comes amid disclosures of information indicating that the missing airplane could have flown for several hours after the last reading from its transponder, a radio transmitter in the cockpit that communicates with ground radar. That raises the possibility that the plane could have ended up thousands of miles from its last confirmed contact over Southeast Asia.

The disappearance of the jetliner and the 239 people on board nearly a week ago has turned into one of the biggest mysteries in aviation history, befuddling industry experts and government officials. Authorities still don't know where the plane is or what caused it to vanish.

"I, like most of the world, really have never seen anything like this," Marks said of the scale of the search, which involves dozens of ships and planes from a range of countries. "It's pretty incredible."

On the seventh day of efforts to locate the missing Boeing 777-200, here are the latest main developments:

-- Tracking the pings: Malaysian authorities believe they have several "pings" from the airliner's service data system, known as ACARS, transmitted to satellites in the four to five hours after the last transponder signal, suggesting the plane flew to the Indian Ocean, a senior U.S. official told CNN.

That information combined with known radar data and knowledge of fuel range leads officials to believe the plane may have made as far as the Indian ocean, which is in the opposite direction of the plane's original route, from Kuala Lumpur to Beijing.

-- Why Indian Ocean?: Analysts from U.S. intelligence, the Federal Aviation Administration and National Transportation Safety Board have been scouring satellite feeds and, after ascertaining no other flights' transponder data corresponded to the pings, came to the conclusion that they were likely to have come from the missing Malaysian plane, the senior U.S. official said.

"There is probably a significant likelihood" that the aircraft is now on the bottom of the Indian Ocean, the official said, citing information Malaysia has shared with the United States.

Indian search teams are combing large areas of the Andaman and Nicobar Islands, a remote archipelago in the northeast Indian Ocean. Two aircraft are searching land and coastal areas of the island chain from north to south, an Indian military spokesman said Friday, and two coastguard ships have been diverted to search along the islands east coast.

-- Malaysian response: In a statement Friday, Malaysia's Ministry of Transport neither confirmed nor denied the latest reports on the plane's possible path, saying that "the investigation team will not publicly release information until it has been properly verified and corroborated." The ministry said it was continuing to "work closely with the U.S. team, whose officials have been on the ground in Kuala Lumpur to help with the investigation since Sunday

On Thursday, Malaysia Airlines Chief Executive Ahmad Jauhari Yahya said that Rolls-Royce, the maker of the plane's engines, and Boeing had reported that they hadn't received any data transmissions from the plane after 1:07 a.m. Saturday, 14 minutes before the transponder stopped sending information. He was responding to a Wall Street Journal report suggesting the missing plane's engines continued to send data to the ground for hours after contact with the transponder was lost.

The Wall Street Journal subsequently changed its reporting to say that signals from the plane -- giving its location, speed and altitude -- were picked up by communications satellites for at least five hours after it disappeared. The last "ping" came from over water, the newspaper reported, citing unidentified people briefed on the investigation.

-- Another lead: Chinese researchers say they recorded a "seafloor event" in waters around Malaysia and Vietnam about an hour and a half after the missing plane's last known contact. The event was recorded in a non-seismic region situated 116 kilometers (72 miles) northeast of the plane's last confirmed location, the University of Science and Technology of China said.

"Judging from the time and location of the two events, the seafloor event may have been caused by MH370 crashing into the sea," said a statement posted on the university's website.