The unprecedented hunt for a missing Malaysia Airlines jet expanded northwest to Kazakhstan and south into the desolate reaches of the Indian Ocean after Malaysian authorities concluded the plane was deliberately diverted by someone with considerable flying experience. A summary of the latest information on the search for the plane and the investigation into what happened:
The Boeing 777's Aircraft and Communications Addressing and Reporting System, or ACARS, last transmitted at 1:07 a.m., about 40 minutes after takeoff. ACARS sends information about the jet's engines and other data to the airline. The transponder, which identifies the plane to commercial radar systems, was shut down about 15 minutes later.
The final, reassuring words from the cockpit - "All right, good night" - were believed to have been spoken by co-pilot Fariq Abdul Hamid, according to Malaysia Airlines CEO Ahmad Jauhari Yahya.
After its communications ceased, the plane turned west and crossed the Malay Peninsula. Military radar detected it moving along a known flight route until it was several hundred miles (kilometers) offshore.
Even disabled, ACARS emits hourly pulses that are recorded by a satellite, and Flight 370's last "ping" was sent at 8:11 a.m. The location of the plane could only be determined in a broad arc from the satellite, which places the jet as far north as Kazakhstan in Central Asia or far into the southern Indian Ocean. The plane at that point would have been near the limit of its on-board fuel supply.
Malaysia's government sent diplomatic cables to relevant countries to seek their help with the search and ask for any radar data that might help narrow the task. Twenty-six countries are involved in the search.
The northern search corridor includes countries with busy airspace that likely would have noticed an unidentified aircraft in their territory. China, India and Pakistan are among the nations that say they have seen no sign of the plane.
Australia is leading the search efforts in the southern Indian Ocean. It has sent two AP-3C Orion aircraft, one of which is searching north and west of the Cocos Islands. Two more search aircraft will be deployed by Tuesday.
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. Experts say if the plane crashed there, finding the wreckage could take months or longer, if it is found at all. Establishing what happened with any degree of certainty will require evidence from cockpit voice recordings and the flight-data recorders, which are on board the plane.
The investigation is focusing on the plane being deliberately diverted by the pilots or someone on board with considerable flying experience. Police seized a flight simulator from the pilot's home on Saturday and also searched the co-pilot's home. Investigators are checking backgrounds of all 227 passengers and 12 crew members, as well as the ground crew, to see if links to terrorists, personal problems or psychological issues could be factors. But authorities are being tight-lipped about what they've learned so far.
The whereabouts of the plane is only one question still unanswered. The investigators are also considering: If the two pilots were involved in the disappearance, were they working together or alone, or with one or more of the passengers or crew? Did they fly the plane under duress or of their own will? Did one or more of the passengers manage to break into the cockpit or use the threat of violence to gain entry and then seize the plane? And what possible motive could there be for diverting the jet?