If i am not wrong, all flights have to make radio communication
once they reach a certain distance near Singapore. That is for the
ATC to stack them up for landing. At that distance I believe they
would still require vectors to final from ATC. SO IF some terrorist
hijacked some flight off Singapore n tries to crash into Singapore,
the ATC would know, since the terrorist most likely wouldnt
communicate with ATC when required to.
Once a course change is detected, and there is no communication
with the aircraft, I believe the proper alerts would be
sounded.
