I am going to go out on what I think is a safe limb and theorize that the Malaysia Airlines flight MH370 did not crash and is currently hidden somewhere in western China.
Today Reuters published the article “From his Pakistan hideout, Uighur leader vows revenge on China”:

Entrenched in secret mountain bases on Pakistan’s border with Afghanistan, Uighur fighters are gearing up for retribution against China to avenge the deaths of comrades in Beijing’s crackdown on a separatist movement, their leader told Reuters.

China, Pakistan’s only major ally in the region, has long urged Islamabad to weed out what it says are militants from its western region of Xinjiang, who are holed up in a lawless tribal belt, home to a lethal mix of militant groups, including the Taliban and al Qaeda. …

There has been almost constant tension between the Han Chinese and the Uighurs since the 1750s. This NPR interview provides a very brief summary of the region’s geopolitical and economic importance and its cultural/religious differences. A chronology of key events related to the region covering from the 2009 riots to the March 2014 terrorist knife attack in Kunming shows a sharp increase in serious incidents since the beginning of 2013.

Could Uighur rebels be behind this? But why hijack a Malaysian plane? Were the large number of Chinese citizens on the plane a terrorist target? And just how did the hijackers – whoever they are – do it and get away with it?

AP reported that a Malaysian official, who declined to be identified because he is not authorized to brief the media, said only a skilled aviator could navigate the plane the way it was flown after its last confirmed location over the South China Sea. Reuters reported that whoever was piloting the plane seemed to be familiar with navigational routes. A map showing points where the plane was detected is here.

The now-high likelihood that the plane was being piloted by someone with enough skill to both avoid radar detection and maneuver through steep rises, dives, and turns, taken together with what appears to have been a sophisticated, systematic dismantling of transponders and tracking systems, and the new knowledge that the plane was flown for at least several hours after its radar disappearance, is strong evidence that the plane was under control and did not crash, and that points to a deliberate action to divert the plane.

But wouldn’t the passengers have risen up in revolt, like the passengers on 9/11’s Flight 93? I first theorized here that depressurization, if hijackers were prepared for it, would be a highly effective way to immobilize the passengers and in-cabin crew. At best they’d be tethered to their oxygen masks; at worst they would rapidly lose consciousness and die.

The New York Times reported today that radar signals recorded by the Malaysian military appeared to show that the missing airliner climbed to 45,000 feet, above the approved altitude limit for a Boeing 777-200, and noted:

An Asia-based pilot of a Boeing 777-200, who asked not to be identified because he was not authorized to speak to reporters, said an ascent above the plane’s service limit of 43,100 feet, along with a depressurized cabin, could have rendered the passengers and crew unconscious, and could be a deliberate maneuver by a pilot or a hijacker.

With respect to landing, one official noted that it would take a long runway to land a 777-200, and added that, although the radius that the plane could have flown extends into South Asia, “the idea it could cross into Indian airspace and not get picked up made no sense.”

It made no sense because the assumption was made that the hijackers of the flight wouldn’t attempt it because the plane would get picked up on military radar. But think about it: what did the Malaysian military do?

The erratic movements of the aircraft after it diverted course and flew over the country also raise questions about why the military did not respond to the flight emergency. Malaysian officials have acknowledged that military radar may have detected the plane, but have said they took no action because it did not appear hostile. (emphasis mine)

If the plane climbed to a high enough altitude, and were flying along a known flight navigation route, it would have appeared unthreatening to Bangladesh, India, and Bhutan, the 3 countries whose borders would very rapidly be crossed while heading north to China. Once safely over China’s airspace, the plane could have quickly dropped out of sight of civilian Primary Surveillance Radar, as it did over Malaysia, but it may not have needed to: ground radar coverage in western China is spotty to non-existent due to mountainous terrain and sparse population. (And remember, the plane is not “visible” via other methods.)  Alternatively – and more dramatically – it could have suddenly and sharply descended at the northern edge of Bhutan, as if it were going to land at Paro International Airport, about 20 miles from the China border. The tiny airport nestled among the steep mountains of the Himalayas is said to be the most dangerous in the world, requiring a steep descent. As of 2011, only 8 pilots in the world were allowed to land there. By the time any ground response would have been mobilized, though, the plane would have veered off well into Chinese airspace. As we’ve seen, it’s very easy for a plane to evade detection with some bold planning, and it probably would be easy to continue to do so in a vast, sparsely populated part of China.

The real danger lies in what the plane could be used for. For example, if secretly repainted with Air China’s (or another airline’s) livery and logo, and outfitted with a new transponder, it could be made into a weapon of mass destruction, fly into Beijing airspace, and it’s very possible that no one in a fast-paced air traffic control environment would notice anything was amiss until it was much too late.

Again, it’s just a theory. I hope that the last part of this one is not proved right.