The facts and the theories in the case of the missing Malaysia Airlines jet

With very few clues and a number of odd details, right now the fate of the 239 passengers and crew on board is unknown. Here's how things stand right now:

Flight MH370, a Boeing 777-200 ER, departed Kuala Lumpur International Airport at 00:41 MST, and was due to arrive in Beijing Capital International Airport six hours later.

The plane's transponder, which transmits its location and identification, suddenly went dark less than an hour after take-off while the plane was cruising at a steady 35,000 feet.

The Malaysian military says their radar indicated that the plane may have been turning around before vanishing.

No distress call was received, and no debris has been found. Two oil slicks found near where the plane vanished are said to be unrelated.

Two passengers with stolen passports were on board the plane, bound for Beijing, Amsterdam and then on to other European cities. Malaysian authorities have said these two passengers were not of Asian appearance.

Five passengers checked into the flight from Kuala Lumpur to Beijing, but did not board. Malaysian authorities said their baggage was unloaded before take-off.

Officials say that the cockpit door on the flight would have been locked.

A sudden twin-engine failure: While generally considered a safe plane, the Boeing 777-200 ER has had some problems. For example, a British Airways 777-200 ER crashed just before landing at Heathrow in 2008 due to ice crystals in the fuel lines. Rolls Royce, the engine manufacturer, later said it had fixed the problem. In any case, even if both engines iced or caught fire, the plane should have been able to glide toward the sea, and the pilots should have had plenty of time to send a distress call.

A weather-related incident: Although no bad weather had been reported, pockets of clear air turbulence are not uncommon over the Pacific. Air France Flight 447 vanished in 2009 on its way from Rio de Janeiro to Paris after hitting an area of turbulence in bad weather; although pilots took control of the plane from the auto-pilot, they apparently did not send a distress call. Nevertheless, a pocket of turbulence in clear weather strong enough to bring down an airliner would be unprecedented. Similarly, a Boeing 777 is designed to be able to withstand a lightning strike. In any case, the failure to find any debris is puzzling — normally, the ocean's surface would be littered with seats, doors and other detritus had the plane crashed into the sea.

A catastrophic failure of the frame or wings of the airplane: Malaysia's military said the plane might have started to turn around before vanishing from radar screens. Could the plane have encountered mechanical problems, lost height suddenly and started to try to return home? This could be a reason why search aircraft might not be looking in the right area for debris. But in such an event, pilots would normally have time to send a distress call. No such call was logged. Alternatively, the plane could have disintegrated in mid-air. This is very unlikely when a plane is cruising at a steady altitude, but it could explain the lack of a distress call. Even then, the absence of any debris in the area where it vanished is puzzling.

Pilot suicide: Pilot suicide was cited as a possible cause behind the crash of a Silk Air flight from Jakarta to Singapore in 1997 that killed 104 people; it was also a possible reason for the crash of an Egypt Air flight from Los Angeles to Cairo in 1999, killing 218 people. But investigations into both crashes were inconclusive, and no evidence has emerged that this could have been behind the latest incident.

A bomb: Malaysian authorities say five men checked in for the flight but did not board, raising the possibility someone may have planted a bomb on board. But Azharuddin Abdul Rahman, head of Malaysia's civil aviation, insisted that all the baggage loaded on the plane had been properly checked, and any bags belonging to no-show passengers had been off-loaded — apparently without significantly delaying the plane's departure. A bomb could have caused sudden and fatal decompression, and such a sudden loss of altitude that the transponder's signal was no longer visible to the nearest receiving station. But why would a terrorist group not issue a statement claiming that they had carried out the attack?

A bungled hijack: The fact that two passengers apparently boarded the plane with stolen passports prompted speculation about a possible hijack. A bungled hijack could also have explained the plane's apparent attempt to turn before vanishing: If the plane departed from its route before crashing, that might explain why the debris has been hard to locate. Hijackers could have turned off the plane's transponder, although the plane should in theory still have been visible on primary radar. Again, though, the lack of a statement from a would-be hijack group is puzzling. And why would a Malaysian plane bound for China be a target for hijackers? And how did they get around the locked cockpit door?

What's especially disheartening about this case is that it's not entirely clear when, or even if, we'll find out more information that could lead to a fuller picture of what happened. It took almost three years for those investigating Air France Flight 447 to come to a conclusion, and that was only possible because, after two years of looking, they found the black box. With no sign of any debris yet, that stage hasn't even begun.

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Taylor anchors WorldViews, the Washington Post's foreign news blog; Washington Post staff writer Simon Denyer contributed to this report.