The kidnapping theory is a very interesting one. Especially when you look at how far away Beijing is, and then draw a circle with the same size radius and look at the countries that are inside of that circle (as places that would use a similar amount of fuel to get to). Very interesting.

ETA
But I also feel very frustrated as I'm certain there must be other (possibly much further away) countries with accurate (but secret) radar & satellite data who can't share it because (*ahem*) that would be admitting they are watching parts of the world that are none of their business. (A bit like China made a huge show of "announcing" that they were "deploying" satellites several days after the disappearance, like there was some big red switch that had to be turned on, & then nearly immediately reported something of interest). Tragic that the lives of a couple of hundred people could be hanging in the balance.