We're updating this post as new information comes in.
There's still no sign of Malaysia Airlines Flight 370 or the 239 people on board.
The plane went missing March 8, less than an hour after taking off from Kuala Lumpur on what was supposed to be about a six-hour flight to Beijing.
It's thought the jet turned west, crossing back over Malaysia, before heading either north or south for at least six more hours. The main reason authorities don't know more about where the plane went: They say its tracking gear was turned off or disabled.
Among today's news about the jet's disappearance and the massive search that's underway:
-- Reuters reported early Monday that there is "mounting evidence the plane's disappearance was meticulously planned." The news service went on to write that "suspicions of hijacking or sabotage hardened further after it was confirmed the last radio message from the cockpit — an informal 'all right, good night' — was spoken after someone had begun disabling one of the plane's automatic tracking systems."
But later in the day, Reuters writes, Malaysia Airlines CEO Ahmad Jauhari Yahya "told a news conference that it was unclear exactly when one of the plane's automatic tracking systems had been disabled, appearing to contradict the weekend comments of government ministers."
"Defense Minister Hishammuddin Hussein, who is also Malaysia's acting minister of transportation, appeared to give a crucial clue pointing to the possible complicity of the pilots when he said at a news conference on Sunday that the communications system had been 'disabled' at 1:07 a.m. on March 8, before someone in the cockpit gave a verbal signoff to air traffic controllers here on the outskirts of Kuala Lumpur.
"But Ahmad Jauhari Yahya, the chief executive of Malaysia Airlines, clarified at a news conference early Monday evening that the communications system, known as an Aircraft Communications Addressing and Reporting System, had worked normally at 1:07 but then failed to send its next regularly scheduled update at 1:37 a.m."
(We updated with the information about the airline executive's statement at 9:45 a.m. ET. This development underscores, again, how even information released by officials in a position to know about the investigation can change. We'll continue to sort through what's out there and update.)
As for the "all right, good night" sign off, airline officials said Monday that they believe those words were spoken by co-pilot Fariq Abdul Hamid.
That does not necessarily mean, of course, that the co-pilot disabled the tracking system. According to Reuters:
"The informal hand-off went against standard radio procedures, which would have called for the speaker to read back instructions for contacting the next control centre and include the aircraft's call sign, said Hugh Dibley, a former British Airways pilot and a Fellow of the Royal Aeronautical Society.
"Investigators are likely to examine the recording for any signs of psychological stress and to determine the speaker's identity to confirm whether the flight deck had been taken over by hijackers or the pilot himself was involved, he said."
Greg Waldron, Asia managing editor at the news site Flight Global, tells NPR's Frank Langfitt that whoever turned off some of the tracking systems "seemed to have a very astute knowledge on how to completely shut down the entire communications system on this type of aircraft. It shows a very comprehensive knowledge of the 777, a terrifying amount of knowledge to be honest."
According to the BBC, "police have searched the homes of Captain Zaharie Shah and co-pilot Fariq Abdul Hamid. A flight simulator taken from the captain's home was being reassembled and examined at police headquarters, officials said."
-- The search is expanding northwest into Central Asia and south across much of the Indian Ocean, NPR's Langfitt reports from Shanghai.
The Wall Street Journal writes that "Malaysia has requested radar information and search assets from the 26 countries involved" and is "coordinating with countries as diverse as Laos and the U.S. to search the northern corridor between Thailand and the border of Turkmenistan and Kazakhstan."
Australia, Bloomberg News adds, has taken the lead in the search to the south.