Malaysian Flight MH370 Disappears: How is this possible in 21st century ?

How rarely does it happen that something (as big as a plane) goes on missing and cannot be found by the 
21st century technology.

Read more about the missing plane  here:

http://rt.com/op-edge/malaysia-passenger-plane-missing-309/

http://edition.cnn.com/2014/03/21/world/asia/malaysia-airlines-plane/