[Yosemitest]

MH370 Didn't need to shadow the same aircraft all the way.
The shadowing was needed crossing the border to the country's airspace, although the longer you do one aircraft, the easier it is as you change airspace from controller to controller.
The pilot's experience over the years of flying that airspace helps him to know where the radar blind spots are, in those routes.
He could have used two separate aircraft for the two border crossings, shadowing them from slightly behind and above, but below could have been done also.
Below is harder due to wake turbulence.
The hardest part is keeping the aircraft in sight, that you are shadowing, and below and slightly to one side is also possible, but out of sight of the passengers in the aircraft you are shadowing, is very important.

[GOPJ]

Here’s one you might be interested in:

Questions Over Absence of Cellphone Calls From Missing Flight’s Passengers

http://www.nytimes.com/2014/03/18/world/asia/questions-over-absence-of-cellphone-calls-from-missing-passengers.html

My theory is the plane was taken to 45,000 feet, depressurized around 1 AM and all passengers were killed before they had a chance to call anyone..