It has been six days since Malaysia Airlines flight #MH370 disappeared from radar an hour into its flight to Beijing, and investigators have found no solid evidence indicating what may have happened to the plane or where it is now.
The lack of information has spawned plenty of theories, particularly on the internet, with little or no evidence to back them up.
Excluding the "captured by aliens" theory, here are five of the most repeated theories of what happened to flight MH370:
1) The Plane Was Stolen But Crashed into the Ocean
This version is a sort of botched hijack theory, but it doesn't explain why it would be hijacked and then crashed. No group has claimed it has hijacked the plane.
2) The Plane Was Stolen and Is Being Concealed Somewhere
Speculation has mounted in the past day or two that the plane did not crash or explode and fall into the ocean.
Instead, some think the plane made it to a strip of land where it is now being concealed for a future purpose, likely a nefarious one. Vietnam, Pakistan, Yemen and the island Diego Garcia, which houses a U.S. Naval Support station, have all been named as possible landing strips.
3) Mechanical Failure or Fire Cut Electricity, Oxygen to Plane
Analysts have said since the plane's disappearance that a catastrophic mechanical failure or fire could have caused the plane to lose electricity and/or oxygen, which would explain the lack of a mayday call from the pilot's.
If the plane was still working, it could have flown on autopilot for thousands more feet before steadily descending into the ocean. Or a mechanical failure could have caused the plane to nosedive immediately.
The Boeing 777 has many safeguards against complete catastrophic failure, but experts say it remains a possibility.
4) The Jet Exploded in Mid-Air
Because there has been no debris found floating in the ocean, some theorists have said the plane could have broken up at 35,000 feet, spreading miniscule pieces of wreckage into the sea that would be too difficult to spot. A bomb could have cause the plane to disintegrate mid-air.
5) The Plane Was Shot Down by Another Country's Military
Others have speculated that Flight 370 was accidentally shot down by a missile from another country's military, which did not recognize the plane as a civilian aircraft and fired at it. The United States mistakenly shot down an Iranian passenger plane in the 1980s, an incident referred to frequently in recent days in speculation about MH370.