What caused Malaysian jet’s crash?

A 12-mile-long oil slick spotted between Malaysia and Vietnam on Saturday afternoon is thought to be the first sign that a missing Malaysia Airlines flight with 239 people aboard went down in the waters between southernmost Vietnam and northern Malaysia, according to Vietnam’s director of civil aviation.
“An AN26 aircraft of the Vietnam Navy has discovered an oil slick about 20 km in the search area, which is suspected of being a crashed Boeing aircraft,” said Lai Xuan Thanh, the director of the Civil Aviation Administration of Vietnam.
The discovery came as Vietnam, Malaysia, China, Singapore and the Philippines staged an intensive search for the missing aircraft that vanished after taking off from Kuala Lumpur early Saturday morning. It was bound for Beijing.
US military officials said the destroyer, the USS Pinckney, is currently en route to the southern coast of Vietnam to help search for the missing jet. While there was no information of a possible bomb or terror attack behind the missing plane, Malaysia is studying all possibilities, Acting Transport Minister Hishammuddin Hussein told reporters.
The majority of the passengers were Chinese. Three US citizens and four Indians were also on the ill-fated flight.
“Malaysian Air’s safety records have been very good,” said Mohshin Aziz, an analyst at Maybank Investment Bank, describing the Boeing 777 as the safest aircraft in the world.
Arab News aviation expert adds: There is too much confusion and if one is honest the disappearance of Flight 370 has no precedent.
While one cannot second guess what happened for this catastrophic situation to occur, it is pretty much inexplicable that 24 hours later no one knows where the aircraft or its wreckage lies. Both the Flight Data Recorder and the Cockpit Voice Recorder, known popularly as black boxes, and can withstand crashes have electronic pulses that can be tracked.
What is most surprising is the absence of and reaction from the pilots. They have an emergency transponder on a 7700 frequency which is merely a press of a button away.
While the Go team of the National Transportation Safety Board will be winging its way to the site, the three most likely scenarios are:
Catastrophic failure caused by an explosive device.(Possible)
A sudden magnetic field that destroyed all electronic functions. (Not probable since there exists no precedent.)
A deliberate attempt by the pilot or co-pilot to send the aircraft under duress. (Possible)
The list is endless, but never has a wide-body disappeared on a clear day without so much as a trace.