It is well known that China has been experimenting with quantum singularity and tachyon accelerators over the East China Sea, and it seems to me that was happened was that Flight MH370 entered into some kind of portal that accelerated it to the speed of light, and it travelled that speed for a few seconds. As Einstein's theory of general relatively proves, to us it seems like the disappearance of MH370 and the crash of MH17 happened four months apart, but to those on board, travelling at the speed of light, it was just mere seconds. Obviously, the plane could not survive travelling at such a speed and immediately broke up.
Now, it was known that MH370 was going to reappear somewhere some time, and personally I think it probably reappeared somewhere over the Gobi desert. The Chinese, working together with the Americans, then scooped up all the wreckage and bodies, dropped it over Eastern Ukraine and created the "phantom missile theory".
The real passengers of MH17 were probably killed and taken somewhere to be buried before even getting on the plane. The Russians are in on it to, which is why they are going to keep the bodies.