just to clarify, "map shift" refers to a situation where, for a number of possible reasons, the IRS/FMS system has not updated the aircrafts position properly, therefore the aircraft position displayed on the nav display is incorrect. However, it looks correct.
An aircraft programmed with a lat and long to hit a building experiencing a small map shift ( a common occurence) would in fact miss the building. So simply using the FMS and autopilot is not reliable enough.
The fact no-one picked this up kind of demonstrates the difference between the PC simmers knowledge of aircraft systems and the real world.
I say this not to put anyone down but simply to confirm that a knowledge of the aeroplane gained through a PC sim, no matter how seemingly detailed, will be lacking in numerous ways that the PC simmer will not even be aware of.
A little knowledge is a dangerous thing......................(mostly to the potential terrorist in the above example.)