UPDATE: Reuters

Communications satellites picked up faint electronic pulses from Malaysia Airlines Flight 370 after it went missing on Saturday, but the signals gave no information about where the stray jet was heading and little else about its fate, two sources close to the investigation said on Thursday.

The “pings” indicated that the aircraft’s maintenance troubleshooting systems were switched on and ready to communicate with satellites as needed. But no data links were opened because the companies involved had not subscribed to that level of service from the satellite operator, the sources said.

Original Post
The Wall Street Journal reports that Malaysia Flight 370 flew on for four hours after it lost contact with air traffic controllers. Ominous.

That would put it somewhere in this area:

From Airchive:

Had the airplane maintained a 550mph cruise speed it could have traveled up to 2,200NM before its engines stopped transmitting data. The means the airplane could have wound up as far south as Australia, as far west as western India, into upper China, and nearly to Papau New Guinea in the east.

Apparently the Rolls Royce engines (via @rahorvath) collect data on how the engines are functioning and transmits it via shortwave radio(?) every thirty minutes (via @southpaw) and those transmissions continued after the plane’s transponders stopped.*

Back to the WSJ:

U.S. counterterrorism officials are pursuing the possibility that a pilot or someone else on board the plane may have diverted it toward an undisclosed location after intentionally turning off the jetliner’s transponders to avoid radar detection, according to one person tracking the probe.

[...]

At one briefing, according to this person, officials were told investigators are actively pursuing the notion that the plane was diverted ‘with the intention of using it later for another purpose.’

It is unclear to me how the plane avoided other radar stations after the transponder went dark. But the pilot did have the capability to turn it off.

*See also the continuing discussion at @7im