The disappearance of Malaysia Airlines Flight 370 has generated dozens of theories on where it is now, from the Indian Ocean to the South China Sea, and how it vanished. Here's a rundown of what we know and what we don't, along with clues and theories about what happened to the Malaysia Airlines jetliner:
* LAST CONTACT: Flight MH370 last communicated with air traffic control on March 8 east of Malaysia, and that area of the South China Sea between Malaysia and Vietnam initially was the focus of the search. Many experts assumed the plane had suffered a sudden catastrophic event because pilots didn't alert ground control before it vanished from radar screens.
However, nothing was found there or farther north in the Gulf of Thailand. Within 18 hours, Malaysian authorities said they believed the plane may have tried to turn back, and search planes and vessels were sent to the Strait of Malacca, on the other side of Malaysia.
* EXPANDED SEARCH: The search moved into the Indian Ocean on Friday after U.S. officials said the plane had sent signals to satellites for hours after its last contact with air traffic control. The U.S. Navy moved one of its ships in the Strait of Malacca. India has said it is searching hundreds of small, uninhabited islands in the Andaman Sea more than 700 miles (1,126 kilometers) west of the plane's last known position.
* SEISMIC REPORT: A Chinese university says it detected a seismic event in a ''non-seismic zone'' near the spot in the South China Sea where the plane lost contact with air traffic control. U.S. geologists said the event was a 2.8-magnitude earthquake off the coast of Indonesia, and said a quake resulting from a plane crash was improbable.
* `HUMAN INTERVENTION': A U.S. official said in Washington that investigators are examining the possibility of ''human intervention'' and that the disappearance may have been ''an act of piracy.'' The key evidence behind the theory is the fact that contact with the Boeing 777's transponder stopped several minutes before a messaging system on the jet stopped working. Some experts are leaning toward the theory that pilots or someone else with aviation experience deliberately veered the plane off course. They find it hard to believe that a modern jetliner like the 777 would experience a total electronic failure that left the plane unable to communicate,