 FACT: It is impossible for the terrorists to have changed the  Instrument Landing System (ILS) 200 feet lower to make the Windsor  aircraft crash. ILS is a fixed system of radio signals and would be  impossible to just enter a code into a computer to make the aircraft  think that its 200 feet higher than it actually is. The position of  the ground and runway never changes, nor needs to be changed, so an  ILS that can have the glide slope altered is inherently unsafe.  Furthermore, the aircraft itself would have an altimeter so the  pilots would know their altitude.