KUALA LUMPUR, Malaysia (AP) -- When someone at the controls calmly said the last words heard from the missing Malaysian jetliner, one of the Boeing 777's communications systems had already been disabled, authorities said, adding to suspicions that one or both of the pilots were involved in the disappearance of the flight.
Investigators also were examining a flight simulator confiscated from the home of one of the pilots and dug through the background of all 239 people on board, as well as the ground crew that serviced the plane.
The Malaysia Airlines jet took off from Kuala Lumpur in the wee hours of March 8, headed to Beijing. On Saturday, the Malaysian government announced findings that strongly suggested the plane was deliberately diverted and may have flown as far north as Central Asia or south into the vast reaches of the Indian Ocean.
Authorities have said someone on board the plane first disabled one of its communications systems -- the Aircraft and Communications Addressing and Reporting System, or ACARS -- about 40 minutes after takeoff. The ACARS equipment sends information about the jet's engines and other data to the airline.
About 14 minutes later, the transponder that identifies the plane to commercial radar systems was also shut down. The fact that both systems went dark separately offered strong evidence that the plane's disappearance was deliberate.
On Sunday, Malaysian Defense Minister Hishammuddin Hussein told a news conference that the final, reassuring words from the cockpit -- "All right, good night" -- were spoken to air traffic controllers after the ACARS system was shut off. Whoever spoke did not mention any trouble on board.
Air force Maj. Gen. Affendi Buang told reporters he did not know whether it was the pilot or co-pilot who spoke to air traffic controllers.
Given the expanse of land and water that might need to be searched, finding the wreckage could take months or longer. Or it might never be located. Establishing what happened with any degree of certainty will probably require evidence from cockpit voice recordings and the plane's flight-data recorders.
The search area now includes 11 countries the plane might have flown over, Hishammuddin said, adding that the number of countries involved in the operation had increased from 14 to 25.
"The search was already a highly complex, multinational effort," he said. "It has now become even more difficult."
The search effort initially focused on the relatively shallow waters of the South China Sea and the Strait of Malacca, where the plane was first thought to be. Hishammuddin said he has asked governments to hand over sensitive radar and satellite data to try to get a better idea of the plane's final movements.
With more information, he said, the search zone could be narrowed "to an area that is more feasible."
Investigators have said the last known position of the plane could be anywhere on a huge arc spanning from Kazakhstan down to the southern stretches of the Indian Ocean. Given that a northern route would have sent the plane over countries with busy airspace, most experts say the person in control of the aircraft would more likely have chosen to go south. The southern Indian Ocean is the world's third-deepest and one of the most remote stretches of water in the world, with little radar coverage.
Australia has a powerful military radar system with an approximate range of 3,000 kilometers (1,900 miles) used to monitor the Indian Ocean west of the country. But the radar would have to have been pointed in the right direction at the right time to have picked up detailed flight activity, said John Blaxland of the Australian National University's Strategic and Defence Studies Centre.
Without any alarms triggered at the time, the radar data probably would have recorded at most a blip on a screen, which likely wouldn't provide enough information to track the plane, Blaxland said Monday.
"So to expect that's going to deliver some kind of miraculous tracking of an aircraft over a week ago ... I think we might be a bit disappointed," Blaxland said.
Australian Prime Minister Tony Abbott said he will speak with Malaysian officials Monday to see if they wanted additional search help.
Asked whether any Australian agency had picked up any information suggesting the plane flew near Australia, Abbott said: "I don't have any information to that effect, but all of our agencies that could possibly help in this area are scouring their data to see if there's anything they can add to the understanding of this mystery."